Do you think I'm crazy or would you think the same?

Ok so my husbands mom died when he was 8 and his dad married his mom's best friend when he was 10 and moved her and her daughter in. My husband hates his step mom says it's not his mom and will never be his mom. He use to fight with his step sister all the time is what they both say and that they didn't start getting along until high school years when he dropped out about Jr year anyways no he babies his step sister she is married and her husband does nothing to help her so she calls my husband and he jumps to her every need even when I tell him no. Well Friday night her and her husband were having problems so she came over to our house even though I've been sick and asked my husband to tell her no... her 3 kids are super messy and never help my kids clean up so it's irritating having them over. But my husband didn't tell her no and caused a fight with me and him. She ended up staying the night with her 3 kids and my husband told me she wanted to go to the bar I said no I'm not watch all 5 kids my 2 and her 3 so they can go to the bar. Well I went to bed at 9 with my 2 year old daughter and my son went to bed as well she put her kids in my kids room to sleep and they stayed up drinking. Well the next morning when we all woke up she had a huge fresh hickey on her neck. That looks bad right she was with my husband her step brother all night and then magically has a hickey!!! Ya I flipped out on my husband asked if he was fucking her and he said no that he honestly has no idea how she got it. And she said the same thing has no idea how she got it. And you can see teeth marks like is is truly a hickey. So the truth comes out that they went to the bar after the kids were asleep after I asked my husband not to and he said it had to have happened there because she went out to smoke alot but I really don't see that going down who sucks on someone they barley know at a bar just seems fishy to me. Like I honestly want to believe my husband but deep down I can't it just looks bad. But part of me feels hormonal and crazy but the other part feels sain and rational.... I need opinions oh I forgot to mention that I knew her 3 years before my husband and not once did she mention him or that she even had a step brother nothing. Then all a sudden a year ago when her and her husband start having problems she won't leave him alone and will always tell him how much she loves and appreciates him.