I kissed my brother's wife?

I was over my brother's house hanging out when he had to leave for work. I was going to leave too but his wife begged me to stay saying she was lonely. I stayed and she started seducing me she told me my brother and her have been having problems and she wants a divorce but he refuses to accept it's over between them. She said she is tired of being sexually deprived and said that she has had sex in 3 years since she refused to sleep with her saying it was boring. She told me how she wanted to sleep with me and she always thought i was hot. She showed me her boobs and we kissed. I stopped myself before things could go any farther regretting that i even kissed her. I don't know if i should believe her she seemed sincere but they have always gotten along when I've been around them. Should i tell my brother?