Jealousy, yes, normal. It is alien, unwanted by us. I admit my humanity by still wanting to bash his girlfriend in the head with a bat (of course I won't, but the feeling is there). Shake her hand? I think not - I guess I am not that evolved, and I'm ok with that.
I am sorry about your DS...I remember getting the kids established with their own IC before the divorce was final, so they had someone outside of the fray to talk to. They have both adjusted well....even though my S14 has told me in confidence that he will never understand why his father made the decisions he did, and wishes he would at least live alone rather than with the girlfriend and her 4 kids. I have come to look at it through my own familiar lens - there were many decisions that my own parents made that I didn't agree with or downright hated. It didn't make me love them any less, but I used it as a lesson learned.
So, what are your plans? With the kids? More importantly, when you are on your own?
I'm surprised that I have had to shake myself up a bit (so easy to get into a rut and just sit around and do nothing) - so I went to meetup and found a book club and an artist group for figure drawing, might do a hike in the near future. Something on your bucket list?