Robby who has had an aversion to the whole 'Daddy' thing bc it made him hyper aware of his age.
But that all got flipped on its head after he and Dennis have gotten into a groove with their sexual relationship.
It just happens one night when they're too tired to get all the way undressed but still need to take the edge off. (Also a good orgasm is a great sleep aide).
Lazily making out in bed - Robby laying on his back, an arm around Dennis' shoulders. The younger man is pressing as much of his front side as he can along Robby's left side with one leg hitched on across his hips. Dennis is slowly rolling his hips as Robby pulls him closer by the thigh.
And the thing that took Robby by surprise was it's said so seamlessly, like Dennis regularly says that particular word instead just for the first time. Dennis breaks the kiss and pants hot breath against Robby's neck.
"Daddy-," Dennis just lets the word fall out. It's not a shout or an exclamation, almost a whine. "Feels good. Touch me please."
At that Robby made a surprised choked off noise from the back of his throat. Dennis first sees the wet spot in Robby's briefs get bigger, then meets his eyes. Robby's mouth hanging slightly open.
"Did you like that?" Dennis asks with a nervous smirk.
Robby doesn't really know just yet, so he clears his throat and stammers out, "I-uh".
So Dennis tries again. This time right right into his ear in a raspy whisper. "I've been wanting to call you that. It just finally came out." Dennis plants sweet kisses along his throat, "so confident, so settled, so good at taking care of me. You have really big Daddy energy."
And huh Robby hasn't thought about it as anything other than an age thing. That sudden change in perspective really gets his dick interested.
"Try it again," Robby requests.
Dennis grins, "Yes, Daddy." And this time Robby indulges in it; lets it sink into his bones and doesn't feel guilty about the following pleasure.
"Oh fuck, baby," Robby groans. "I think I like that."
"Good, because I like it too," Dennis holds Robby's chin and kisses him soundly. "And I like making my Daddy happy."
That gets Robby to finally stick his hand in Dennis' underwater to jerk him off. "And I like to make my baby happy."
Robby thinks maybe self discovery doesn't have to be so scary.