It’s time for your son to ‘man-up’ and tell your daughter-in-law that he is involved with another woman. It seems she still cares about his welfare but he doesn’t care about hers. You don’t say how long they’ve been separated, but it reads that it hasn’t been too long, I would have thought he could have done with a bit of breathing space rather than jump into another relationship. Personally, I wouldn’t be the one to tell your daughter in law, that is up to your son. Honestly, it seems so easy these days to walk out of a marriage because mum is there to pick up the pieces. That isn’t a criticism of you, it’s happened to me with one of my daughters.......and yes, I was there to pick up the pieces. No one wants to see their children struggling but it does make me wonder if separation is made too essy.