Thank you for your Question
Your father in law is your Mahram and there is no problem if you have to be in one place with one another. Although it could be quiet uncomfortable to be sleeping in the same room!
But your brother in law is your Namahram and it would be wise to have your own little space.
You should speak to your husband about it and InshaAllah he is able to solve this. Especially because your mental health is very important for your child’s mental health.
Naajiya s jaffery