At this point, I am on the verge of cancelling my wedding and ending my relationship with my fiancé, all because of his 19yo son. In the beginning of our relationship, my fiancé kept his life with his son and his life with me very separate, spending time with only one of us at a time. When I was around, the son did not hang out with us, but I just thought that he was a teen who didn't want to hang out with older people.