Welcome to the site! You are definitely not alone. Disengagement is the only reason I can stay in my relationship, and the general rule is "only do the things you want to do." If it would make you happy to do certain things with them, great! Do those! If you don't want to and/or would resent doing it? Don't do it. I see myself more as an aunt to them and not a parent. And I, too, get out of the house A LOT. And honestly, I kind of like it that way. I know when I'll get quality time with friends or do one of my hobbies, and it keeps my life in better balance. And if you needing to be around the skids ALL THE TIME meant that you couldn't get your workouts in or see friends, then that would lead to a lot of unhealthy stuff anyway. 

Also, I was a step kid growing up and WISH I got more alone time with my bio parent. You may feel like a bad person or selfish, but honestly, it's not a bad or mean thing to allow your partner time with her kids, you know? I think the biggest problem with disengaging arises with there are different expectations about what your role should look like, but if your partner is like "I love you! Have a great time at the gym!"  then everyone is happy and everyone wins.

A couple of things:

1.) They aren't your kids, and it's okay to not see them as your own. Do they see you as their father, or equal to their father? Likely not with 50/50 custody. Take that burden off your soul.

2.) If the kids need to be nagged to do things, that needs to come from your wife. She is their parent. She doesn't nag them because she doesn't want to be the bad guy. So, when they don't do something they are supposed to, tell her. Nag her. Push her to parent her kids. It's disrespectful to you for her to put you in the position of being the bad guy.

3.) If you are child-free (i.e. no biokids), go live your life when you have time to do so! Your wife has a responsibility to be a mother. That is not your responsibility. It is not your burden. Don't feel guilty that when she is preoccupied as a parent that you're off being a child-free adult.

Overall, from the little you've shared, you seem likr a pretty normal stepparent who wants boundaries. And that's entirely fine! These kids have two parents and their respective families. It sounds like you don't hate them, and I assume you treat them decently. There's nothing wrong with not being a "bonus dad", and anyone who says otherwise has WAYYYYYY over-romanticized parenthood.

Ha, so biodad is "very frugal" is he?

I think YOU need to seriously cut back or stop the financial support of these kids. Why should YOU be shelling out so that the biodad gets to be frugal and save his money??

Extremely frugal? Mmhmm. 

Expenses for the skids are not your responsibility.

Q: What would your wife and biodad do if you weren't helping to foot the bill(s)?

A: They would either pay for things themselves or the skids would go without.

As a step parent, you are in NO way obligated to 'fund' the skids. That is up to their bio parents. Anything you decide to pay for is a gift. 

Time to separate finances.  Decide the bills by percentage but don't let it be 50/50 since she has kids to support.  They are taking you for granted.  She is taking you for granted.  Until she feels the pain of you not enabling her not to  pressure her ex, why should she bother. Take that money you would spend on them and invest it. Save it for a glorious trip once they move out.  Do something with it so it's difficult to access it right now.  Kids can suck a wallet dry faster than anything if you allow it.  Now I'm not trying insulting your manhood by saying you can't support them but the point is you shouldn't have to in the first place.  They have two parents that get to decide how to raise them and if they can't afford it then the kids get told no.  That's what intact families do.  That's what poor people do. The kids still survive.  
 

Also , you have the best of two worlds, married and "single" to pursue your hobbies, hang out with friends, chill in the man cave undisturbed.  

I never announced I was disengaging, I just slowly stopped doing extra things. If my husband specifically asks me for help I normally don't mind. The only thing I did vocalize is that if BM asked anything of him that would affect me I wanted to be consulted and to make a decisions as a couple. 

Sometimes when the kids make a mess or leave their undies in the bathroom after showering I just close the door and use the upstairs bathroom until they leave. I also don't clean up after them he pays for a cleaning service every other week. They clean the common areas and bathrooms, back when SS was peeing everywhere but in the toilet I did not clean. I said hey SS made a mess can you give him a peeing tutorial or something. I am lucky that they aren't disgusting food hiding hoarders and try to pick up after themselves most of the time. Still.... sometimes I am annoyed but I think that comes from them not being my biological children. My kid is a tornado that leaves a path of destruction in any room he occupies and I don't feel as I annoyed as when the skids do it.

I also find things to organize or clean sometimes when the kids are here. If we go do family stuff it's because I want to not bc I feel obligated for the sake of my husband. I also see myself as a cool aunt, I care about them but i will give them back to their parent. I did take advise here and there from other posters until I found ways to create my own role in our family, which has changed over the years.

Separating finances after you have been commingling so long might be a little harder to have the conversation with your wife. I don't like to argue so I'd probably say that I need to start saving more bc I realized I'm not on track for the type of retirement I want. If skids have to do with out bc their two parents can't afford it that's too bad.  
 

Your post really resonated with me as I share a lot of your feelings - and I never saw myself posting on forums either but several years ago, I had reached a wall and didn't know what else to do.  This has been a great release, and also interesting to go back and read when that wall starts looming - and have also received some great advice from people who have lived it too.    I have been a stepmom (officially) for almost 10 years.  My SD was 7 and my SS was 12 when I met them, and I have a son who was also 12 at the time.  I think that helped a lot with building a relationship with my SS, as i was able to relate to him plus he and my son were friends prior to me and their dad meeting, so where SS is concerned things have not been too difficult.  SD has been another story - in the beginning she loved me.  My DH, like your wife, has always had a hard time saying no, or having many expectations or boundaries. SS has never been one to push, but SD grew up being led by both her parents to believe that things revolved around her.  It was easier for me to overlook in the beginning, things were new and she was young, and I naively assumed that things would change when we got married and we would become a unified team of parents.   I was wrong about that, haha

As SD for older, her behavior got more obnoxious, and seeing my DH jump to her demands was frustrating.  I was also a SKid growing up, so taking from my experience I thought it would be best to stay out of things as much as I could, not try to discipline, or step in when she was disrespectful, or even put expectations on her.  I eventually started going to DH with my requests, but he would get defensive- once he even told me she was his daughter and he was going to spoil her no matter what!  Naturally our marriage started feeling a strain, and I actually ended up in a depression.  Like you, I felt guilt about my negative feelings, but looking back, I feel like any reasonable person would have negative feelings about things that were going on.  Especially if you don't feel appreciated or even have a voice.  Try not to beat yourself up over that - you are a person too and allowed to have opinions and feelings about what goes on in your household. 

My DH and I reached a point where we almost lost our marriage because I couldn't take things as they were anymore.  By this time SD was a teen and the behavior was definitely not cute, and I felt like it was the one topic DH and I were on completely opposite sides for.  DH actually suggested we go to counseling, and I have to say, it really did help.  We were fortunate in that the counselor was a stepmom so understood the complications that are part of blended families.  But mostly having a 3rd party guiding our conversation helped us see each other's perspective more.  DH came to understand I wasn't trying to be against his daughter, and once he realized he didn't have to defend her, he realized we really both want the same thing - for her to be a respectful, functioning, happy member of the family.  I was able to see that his defensive reaction about her was mainly fear - it seems a lot of divorced parents have that fear that their kids aren't going to want to be with then any more and they overcompensate.    We started making an effort to put ourselves in each other's shoes, and have come very far in our ability to communicate when it comes to our kids. 

My best advice would be for you to have an honest conversation with your wife about how you are feeling, preferably at a time when there hasn't been anything negative going on so that emotions aren't as high - and possibly look into visiting a counselor, at least for a few sessions.  Our story is ongoing and still not easy, even with all our kids now adults and out of the home - but the years since DH and I have been able to start communicating have been much easier to navigate, and definitely haven't felt as lonely and isolating for me.   I wish you the best!

Just stop parenting and paying for children that aren't your own.  

You say that your partner is made of glass.  I guess this means really sensitive.  You need to sit her down and ask if she wants to avoid annoying her ex or her current partner.  It is ridiculous that she expects you to pay for her inability to challenge the children's father.

On the household cores, leave them to your wife.  If you can't bear seeing the mess build up, than put anything left lying around in trash bags and put somewhere out of sight.  And finally, stop asking them to do anything.  Address the issue with your wife and make her deal with it.  If she has to act like a maid to her kids, that's her problem, not yours.

She has to learn how to deal with her children. So often it becomes a divided household of bios against steps, and we are the "bad guys", and get the attitude and are blamed for everything. Because we are the easy targets!

Your choice to disengage so that you can stop being a target is a wise one. But disengagement is different for everyone, and generally depending on your situation, is either very "burning platform" or more on the "disengagement lite" scale. Read around on here about the differing levels. Either you start with an in-depth quiet conversation with your wife when the kids are gone to dads, or you just do not speak of it, you do it. Either way, you are being made to be the source of their pain because you have tried to parent them.

You are simply acting as the head of your household, but you are not being supported in this by your wife, so you must let her be the parent and back off into your other activities. It sucks, but you are experiencing the backlash when they go to her.

As far as finances go, I agree with the others. YOU do not finance HER and BF children. Anything they need comes from the parents.

For me, I am disengaged. If skid needs winter clothes or anything, her parents get ti for her. There is a rare occasion when I do any pick ups or drop offs. I sometimes cook, but never clean. If there is something that she needs to do, it comes from her father. SD15 has betrayed my trust on numerous occasions but we have a friendly relationship otherwise. I keep it surface. I leave her alone. "ask your father" is my refrain. So you can do that more "go ask your mother" is your mantra. When dishes are left or anything, "sweety can you clean this or have Sd15 clean this".

In my situation, we have 50/50 and DH pays child support plus all medicals. And Im counting down the 2 years and 6 months to 18 and graduate high school. Plus driving. However Dh and Toxic Troll Bm do not have a good record of enabling their chidren - SD22 who lives with BM has no license, no job, and isnt in college, yet her life choices are now our fault. So watch out for your wife coddling and enabling and you may have to break the disengagement to battle over enablement.

For the nearly infinite number of situations that can occur in a blended family there are many multiples of infinity ways to address them.

In your case, I would suggest taking the KIS approach. Keep it simple.  Set the the standards of behavior for kids in your home and marriage and enforce those standards.  If the kids choose to violate those standards, they choose to suffer the consequences of those choices.  You decide the consequence and apply it.

Their choice, Stay on that message.

It works just as effectively with Xs, ILs, and anyone else who fails to  stay in their place.

Like  you, my SS-29 has had me as his dad for as long as he can remember. His mom and I married the week before he turned 2yo.   He asked me to adopt him when he was 22yo. We made that happen.  Even now he not infrequently shares with his mom and I that he appreciates that we raised him with enforced standards of behavior and performance. He three younger also out of wedlock Spermidiot spawned half sibs were not raised as he was and one is in prison, another is on the way to prison(it is only a matter of time), and the third is barely keeping her nose above water in her life.  He also recognizes the positive influence enforced standards parenting has provided to his professional life.  He bangs his head against the wall trying to lead the entitled poor performers to deliver effectively.  He is very successful at it, but it drives him nuckin futz.

Welcome by the way.  There are not nearly enough StepDads in the STalk community.  We are half of the SParent population so it would reason that as many of us desire to vent and get support as the SMoms.  I hope that you find this to be a good place to vent, contribute, and to pick up some useful advice and perspective from others who are living the blended family adventure.

Good luck.