Relationships

My husbands brother, my brother in law is cheating on his wife?

I don't particularly like my brother in-laws wife or her sister... Well I CANtT STAND THEM but we are all currently under the same roof with their two kids and our mom. So I know a lot whether I want to or not. Basically, even though we don't get along the least bit (mainly because of her and her sister) it's super awkward. Recently my husbands brother has been gone all night on weekends saying he's staying over his boys house ( no grown man is going to do that unless it is dire lets be honest) almost all of his friends even live in the same area, within walking distance. My mother in law recently told me nonchalantly that he's been with his girlfriend in another city those nights. no joke I though she was kidding, but then he stayed out another night and I asked my husband if she was serious and he said he's known for MONTHS now. I will never say anything but it's so weird hearing him come in the morning kissing his wife saying I love you and I know where he's been. If anything it's not my business but I'm concerned that my husband doesn't care at all he's kind of like "I feel bad for her but that's my brother at the end of the day" understandable. But his dad was a serial cheater with multiple kids out of wedlock. My husband has done questionable things in the past but I know he hasn't cheated on me I don't think his mom would tell me but I don't think she'll let it fly by my head either but still I have my doubts and all this information has me like this O_O has this happened to anyone else?
Updates
+1 y
Their kids are 4 and 6. I believe that is why the mother does not wish to get involved and she loves her remaining (one passed unfortunately) sons too much to break up his family. My husband also has too much loyalty to his remaining brother to say anything.
My husbands brother, my brother in law is cheating on his wife?
Post Opinion