DH told me he talked to OSS. Did he initiate it? No. OSS actually reached out. Really?! For what you may ask: to tell DH that he wouldn't be the one dropping off YSS but that he, OSS, would still like to stop by some time this week to see people and could he borrow the sander. 

Two questions come to mind when DH got to this part:

1. Why would OSS need a sander? He does not live on his own nor has he shown any interest in helping DH with home projects for $$.  Well seems he wants to borrow it to refinish BMs deck. Hmmmmmm

2. Why wouldn't OSS come now if he wants to see people because all the people are here now? Isn't it interesting timing that he wants to stop by during the week he knows DH and YSS are away camping. So "people" must mean DS (cause it sure as hell doesn't mean me).

At least at the point OSS made the request DH must have felt used and spoke to him about no contact, no response, no recognition or contact on holidays/special days by OSS. DH told OSS he was hurt by the lack of recognition. 

The conversation I had with DH did go in a way I could point out to him that despite our "harder" approach with DS, DS keeps on contact/has a good relationship with me and XH and has a better relationship with DH than DH does with his kids. DH puts himself in the beta male position with his kids and has not demonstrated by his behavior what he wants them to do (do as I say, not as I do), so this situation is not surprising. 
I didn't make much headway because DH is now more afraid to piss off the kid that he's an adult and can't be forced to have a relationship (even though it came up whether he even wants one with someone who doesn't hold up their end of it). And DH was all misty after OSS got right back to him after he texted about picking up the sander. (Sigh, he wants something, that's the reason.)