For me it's having a crazy BM in my life. I knew my SO had children when I got involved and that I would have to become a SM but I never wanted her in my life, making trouble and thinking she is the best thing since sliced bread - She is such a bitch!

I think the most difficult things was going into this not quite knowing what to expect, then having it all crash around my feet. I cringe when I hear "you knew what you were getting into" from others. No, no more so than YOU know what's going to happen tomorrow unless of course you're psychic. I truly believe we go into this with the best intentions but because of different factors those are down the drain.

My SK's don't give me the time of day. I have no more impact on them than a stranger on the street. Oh wait, a stranger with an open wallet. Their belief is because both their dad and I work, we are the $$ bags. Their BM doesn't work so never seems to have much $ to spare to help out with extracurriculars and such. The SK's believe that whatever the BM DOES get them, we should match it doubled -- meaning if she buys them a $150 pair of shoes, we should CERTAINLY be able to afford $300 worth of matching Hollister wear. It's a horrible cycle -- mommy says "I can't afford it" so they come to daddy. Daddy feels badly because "their mom won't do anything for them" so goes overboard. Which prompts mommy to say even more frequently "I can't afford it." Rinse, repeat.

And then there's the BM herself. I finally took a stand and told my DH that I have implemented a ZERO CONTACT policy with her. I will not answer the door or the phone when it's her. I will not be in the same vicinity. I will not make "small talk" because it always ends up with her getting shitty with me for one reason or another. In her mind, everything needs to revolve around HER and that's that. She's not someone I'd be friends with in real life, because her personality does not impress me. She's DH's past, not mine so he's the ONLY one who needs to deal with her. I wouldn't hook up with crazy like that.

And lastly, sometimes the toll it has taken on MY children has been difficult for me. The drama of kids with no boundaries or rules (SK's) because "they're only here 2 days a week" vs my children who live in this house full time and have rules and expectations.

The most difficult part for me has been trying to deal with BM's BS. We were good...by no means perfect, but probably as perfect as steplife could've been until she came back.

For me, it is a few things:

1. Coming to terms that because of one stupid little mistake, we have to change our entire lifestyle to accommodate crazy and to have a constant reminder of that slip in judgement.
2. That it's hard enough starting a life together, and now there are so many things we have to do that we never thought we would until much later (wills, prenup, clear financial guidelines etc.)
3. That there's the possibility that because of this, I will leave because I just "don't want to deal with it anymore, no matter how much I may love you." (Because love IS conditional, on respect and equality.)
4. That BM might show up at our house with a shotgun and try to kill me. Or get her exBF to kill me. (Not so much a joke as something that nags at us because of her mental issues.)
5. His family and the people around us pass judgement on our decisions and what we feel is best for us at this time.

What makes it better:
1. The decision to make absolutely no accommodations--she makes none for us, so we will make none for her. In fact, she has been trying to mess with us for a long time so we're actually being super nice that we don't do the same back. A mistake is a mistake is a mistake, but how we deal with fixing it will define us.
2. At least we've become very well versed in the land of law, and honestly, all these things aren't bad and would have to be done sooner or later.
3. We promised to talk it out and work it out. If that's not possible, we will both leave on amicable terms.
4. Not much we can do here, except know that if she tries, at least her ass will go to jail. My death be damned!
5. None of their business, we will not explain ourselves to them unless they can have an adult conversation without criticism or judgement. Our choices are our own.

Hardest part? Going from having ZERO kids to suddenly having TWO, followed by baby BD. DH is a full-time student with a full-time job. Which leaves me the SAH mom/stepmom.
BM is a moron. Not nearly as terrible as some of the BMs here, but not involved in the kids school, has no interest in getting the kids into activities, minimally involved in working with SS7's autism, thinks of herself first and the kids second, won't take the kids for a weekend, will leave them with us whenever possible.
So I'M the one figuring out when the kids have special things going on at school (pajama days, school performances), sending birthday treats to school, handling birthday party invites, etc.
The fact that I have so much responsibility, and I'M the one who really knows what's going on, but I have no rights as far as the kids are concerned.

That being said, I deal with it. The kids are usually good. Their behavior when they're with me (without bioparents) is just about as good as you could expect of kids their ages. I see and hear the differences between when they're with me as opposed to when they're with their parents. They're much more self-sufficient with me; when the bios are around the act like 2yr olds. At the very least I know that I've taught them to age-appropriately care for themselves. I plan to continue to do this. I want them to become independent adults, and they're on their way to that.

For me, the hardest part of being a step is dealing with the emotions of children who have been through a divorce and not knowing what parental household to hang on to. I have no children of my own. I now have 4 step children. I have slowly gained their trust, but BM keeps putting lies into their head and making mine and DH's time more and more difficult... Don't get me wrong, I love my steps as if they were my own, because they are very loving children. They have been raised with respect and manners, they are being taught responsibility and money savings.... they are being taught how to earn what they WANT...

But, having to deal with the transition of 2 households is difficult, they to hear mommy saying bad things about me and daddy... them getting the emotions and attidudes in return...