Ignore the assholes who tell you that you have to "share with the brat".

I have a soaking tub in the bathroom off of our master bedroom. Neither DH nor I have ever used it. But so what - it is not "fair game" for anyone who wants to take a bath. When I do choose to use it I don't want to have to wash out shit from misc. aholes.

I do not want ANYONE in my bedroom/bathroom. This is my personal space. We have a guest room and guest bath - if anyone visits whether overnight or for a few hours this is where they are to go relieve/clean themselves.

My DH's brother for some reason was enthralled with our bathroom. He visited once and upon walking into our home made a beeline for our bathroom where he took a dump. Let me just add that he never did that again.

Perhaps encouraging the kid to be a "big boy" and take a shower instead of a bath might help?

As one biofree stepmom to another, I can tell you that one of the hardest things has been learning to share space with the skid. The best advice I can give you is start setting boundaries right NOW! My SS16 is a dirty, disgusting, smelly, gross teenager who I can barely stand having in my house. When he is there, he gets his room, his bathroom, and I even made special shelves in the pantry and fridge for him. DH stocks it, feeds him, cleans the room, cleans the sheets, cleans the bathroom. It's his kid and he has to take care of it. DH knows the rooms get scrubbed after skid leaves and he knows it's his job. Master bed and bath and other rooms in the house are off limits. At 5 years old, a bath is probably normal but I agree with Sally...access to that room is only with DH supervision, never leave him alone in there and DH and skid make cleaning up after part of the routine. Skid needs to know that he is not allowed in there without DH. You have a long ways to go if he is only 5. DH needs to step up and start taking care of his own and "forgetting" is not an excuse. He should want to keep your private rooms sacred.

your private bathroom needs to remain private. once dh let one of the skids use our master bathroom to relieve himself (he hinted he wanted to use our bathroom), qand then i found my jewellery missing. i questioned him about it and dh took the boy at his word that he did not steal anything. dh sided with the skid and said i must have misplace the ring. the little brat finally fessed up and started crying. it happened that he wanted to punish me for not allowing him to have cookies before dinner.

no need to open all of your house just because there are children. its called setting boundaries. not to set boundaries is the quickest way to becoming a resentful doormat.

For me, this wouldn't be a hill to die on but I do love my privacy. So rules have to be set in place. Boundaries. And be consistent. Just explain to your DH that although you know his child likes taking baths, you would prefer to keep you room and bathroom as your own private space.

SO and I have a rule, Our room is MY space. I am an introvert and like my alone time so all he does in our room is sleep. His space is the living room, SD's space is her bedroom. He isn't "allowed" to hang out in the room if I need alone time. SD has to knock and be invited to stay in there by me if she is to hang out there. In turn we knock on her door as a sign of respect when we are going into her room. She understands that we can go in there if we want without her permission because we are adults but we give her, her space as a sign of respect. She acts up, she loses those privileges. She gets it, and is only 6.

You've been replying to several posts that are MANY years old!   Just FYI ...