How do u deal with your BIL?

It's been a month since I moved out of the comfort of our own house and now staying at my partner's house, with his Mom, sis and brother. I've no worries with his Mom & sis, but his brother is something... Who holds the finances for the house expenses (fyi money is from FIL). It was my in-laws decision to let me stay here so I and my partner can relax and save up for my pregnancy since I am wfh. Since I started living here, I pay no bills... I help with house chores, etc. except cooking coz I am still a bit uncomfy and shy to move around - and tbh, I can only cook basic food as I am not into cooking. Now, it feels so uncomfy when the brother is around... He has this certain attitude of (indirectly) being bossy & do-what-i-say kind of attitude. Makes me not want to talk to him, unless necessary. As much as I want to build good relationship with the brother, I just don't think this will work. How do you deal with it? My partner and FIL just want me to relax, rest after my work shift and not move around too much for my baby's safety but I cannot do that out of guilt knowing that I LIVE in their house - thinking BIL might have something to say. Please let me know your thoughts. I do read every comment. Thanks so much!!