Oh, TeddyIII, my heart aches for you and DS. What an odd young woman XDIL is. Or maybe just a manipulator (to the extreme). It sounds as if she is very unhappy w/in herself, thought the island would make things better, but it didn't, so went home w/ her parents. Unless something happened on that island that you don't know about, then I imagine the problem is w/in her. So sad that is has affected DS and, also, of course, you. Hugs!
"She started divorce proceedings,remarried as soon as possible and had another baby."
Are you saying she was pregnant w/ DS' 2nd child when she left him? Wow. Again, so very sorry.
Maddyone, OMG, I can hardly believe it! Lightening isn't supposed to strike twice, etc. Please don't jump to the conclusion you were "bad parents" though. The issue may have to do w/ sibling dynamics and nothing to do w/ you and DH at all. As you say, it's may be jealousy - he resents it when you have a good relationship w/ his sister and likes it when you're upset w/ her. Or perhaps your son likes to be the "good one" who's there for you when you're having trouble w/ your daughter. But now that you're not, he's unhappy. Or maybe he just thrives on drama, and if his sister isn't creating any, he will. Childish stuff, IMO, but could be just the same. Or hey, you may simply have difficulty dealing w/ AC, many parents do. Hopefully, he'll come around - w/o your D 'having to" cut you off first. Hugs!