My boyfriend got in a fight with his sister now he doesn't want her to see our baby when born?

I know how difficult it can be to remain neutral in the midst of other peoples family feuds. Just do your best to remain neutral and stay out of it. If he insists on being this way and refuses to let her have contact with the baby, then you should probably stay out of that too. I think that his anger will eventually diffuse, and you'll be able to talk some sense into him - but you have to wait until he's obviously ready to listen to some logic, or else he'll just end up getting mad at you too. If the sister tries to contact you, let her know that your trying your best to remain neutral in the situation, and how difficult it is for you to do that. Make it clear that this is not your doing, you're not backing it, and that it's not your decision to make. Hopefully she'll understand and empathize with the position you've been put in. Whatever you do though, always keep it in the back of your mind that you are going to have a relationship with his family for the rest of your life.