X demands full custody because I'm engaged, Part 2

[sleeper]

X's objections have been focused on fiance's children for some time. Fiancé becomes very upset (naturally) when X criticizes her children. Fiancé has raised her children alone, divorced when the youngest was an infant. One of her children has a physical birth defect and she is especially protective of him. As she says ,"I have always had to fight for _____ and protect him."

X's concerns are unfounded and IMHO internally fear driven by her own blended family experiences in her childhood. She didn't want me dating anyone with children (she didn't) and I believe would find fault with any prospective mate's children, IMHO. She insisted to meet with me after Sandyhook because she feared fiance's son would do the same as Adam Lanza.

My problem (and it's totally MY problem) is I can't help but feel I am unwillingly in a position of choosing fiancé or my kids. Sadly, blending our families seemed a breeze a year ago and the kids were excited. Now it's a non-starter. I blame X in large part for the change in our children. X responds the kids never wanted to blend with fiance's kids and they were pretending because they didn't want to hurt my feelings. (she is weaving quite an alternate reality in her head, anything to further her goal)