You don't know what he's told his family about his situation. He could have told them that you are legally separated and very close to a divorce. In today's society, there are some who will not question and/or challenge a family member when they do something wrong.

I remember when my xh did something very similiar to what your h did and his family wanted to question him, but felt it was none of their business. I was reminded that blood is thicker than water and no matter what they do, family generally will rally around them, right or wrong.

Please be careful when discussing things w/his family or friends.

Sit quietly, the answers will reveal themselves when you least expect them to.
The past is gone, the present is a gift and you need to focus on today, allow the future to reveal itself when it is ready.