Welcome to Sober Recovery. You will get great advice here as what you are going through we have also been through.
There is light at the end of the tunnel - for you. I highly suggest you get involved in Alanon. Alanon is a 12-step recovery program for family members of addicts. In Alanon you will find ESH (experience, strength, and hope) and learn techniques on how to deal with your situation.
You are going to be a mom soon (hopefully). Being here and in the rooms of Alanon can give you healthy ideas on how much your child is going to be exposed to the drama of this particular part of your family.
Your mom cannot love you, and that is heart-breaking I am sure. You know in your heart that she also does not love your brother (because she is stubbornly helping him stay sick). Many of us here have experienced that same thing. But that is not the be-all and end-all of your life and your ability to love your husband and your future children in a healthy way.
This problem did not flare up overnight or even in the last year, and so the resolution (for you) is not going to come quickly. But keep coming back and try those Alanon meetings. You are worth it, your husband is worth it, and your future children are worth it!