I certainly avoid any sort of shame when I’ve raised this with my son. My pitch has been to talk about how much he’s grown up and become an independent and reliable kid over the last couple years, and with that he might consider sleeping in his own room at his mom’s. But I’ve been very careful so far to not push it with him.
With my ex, I won’t make it about her at all, or give any hint that I think she’s been driving this. I’d probably say something along the lines of how much I appreciate the bond he has with his mom, that he seems to want the comfort of having his mom close to him when he sleeps, and that he probably won’t move to his own bed unless he gets some encouragement/permission from his mom. Something like that. But I feel like I have to say something, because I’ve kept thinking it was just going to resolve itself, yet it’s been going on for over four years. Everyone with whom I’ve talked about this has commented on how weird it is. Even the therapist I saw during and after my divorce described it as “not healthy.”