Still has a death grip on yesterday...maybe if you swap it out with one of yours he may not notice...

Man child problems AND not over his ex girlfriend.. run away OP, fast and far, run.

burn the "blankie"

That, that is, that is just awkward.

Dump him or it

Having a ''blankie'' or comfort object isn't a problem in itself - a lot of people with anxiety disorders have comfort objects, that doesn't mean they are a ''man-child'' ! It just reassures them. I don't see why it would be stupid. But having the ex's silk nightgown as a comfort object is a little... particular, especially since he's starting a new relationship and is at the stage where he's spending the night at his new girlfriend's. If it was a relationship that lasted for a while, then I guess it may have become his comfort object over time, to replace something more ''childish'' maybe. Seeing everyone's reaction to this ''blankie'' thing, I'm guessing it would make sense that his ex thought it was better that his comfort object be one of her silk nightgown instead of a plush toy, etc. In any case, you'll need to talk to him about it - and if it was changed for something else once, then it can probably be replaced with something else again, since this makes you uncomfortable. ...Maybe go back to something neutral that doesn't belong to anyone, this time.

Really? I've been wondering where my nightgown went!

Well, that's creepy as hell

What a pillock!

Send him away. Tell him he can come back when he gets rid of the ex's night gown.