TBH from what you are describing, this episode sounds like a genuine illness, but we only have your thoughts about the pthers, so there could be a psychologoical element. I know this is uncalled for advice, but as much as you might hate the mum for presumably causing your son (?) a lot of heartache, she will always be the mother of your grandchildren, and as such it will probably help things if you remain civil about her when you are around them (perhaps you are?) She has clearly hurt you a lot too, but you have to remember there are always 2 sides to a story, and no-one knows what goes on in a marriage apart from the peope in it