To start off,is anyone in physical danger in your new situation (including yourself)?
Are you receiving treatment for PTSD?
Is your younger brother living with you in your MIL place now, along with you and spouse?
Does the older brother come to visit?
Is there 1 or 2 older brothers that have molested?

Questions aside, I would hope you are in a place now that protects you from direct contact with your older brother(s) and I also hope your MIL understands what is going on. An older woman can be quite a comfort at times like this. Your spouse can help a great deal as well if he/she fully understands the situation.

Hopefully you can clarify your situation a little better for us so we may know how best to guide you. And see a therapist/psychiatrist if you have not done so yet.