I think when Jon was younger he wet the bed and also Elias should get to take advantage of this when he’s older <3
Making sure Jon goes before bed. Just sitting there and watching, Jon ashamed that he’s a grown man whose own father is monitoring his peeing but achingly aroused, dripping wet whenever Elias mocks him for wetting the bed in his youth.
And maybe one evening he finally cedes and agrees that Jon can take care of himself, a devilish little smirk on his face. Lets Jon get ready for bed and use the bathroom all on his own. Jon climbing into bed beside him (they sleep in the same bed, have for a good few years now. Nothing inappropriate, of course. It’s just the best way for Elias to make sure his son gets enough sleep, to comfort him if he has a nightmare.) Elias pulling Jon into his arms, waiting until Jon has been asleep for hours, slipping his fingers beneath Jon’s shirt, finding his bladder and pressing on it, just hard enough for the urine to flow out of Jon’s pants, a stain spreading on his trousers, Elias’ cock half-hard in his own pants.
In the morning, Jon wakes to discover that he’s soaked them both with pee. Elias grinning, face pressed into the crook of Jon’s neck. A finger slipping into his pants, stroking through his folds, Jon shuddering and gasping in his father’s arms. “Oh? And what’s this, Jon?”
That night, Jon shamefully opens the bathroom door to let Elias “supervise”