I GOT A BOYFRIEND BECAUSE MY CRUSH CONFESSED TO ME SO TAKE THIS HEADCANNON BASED ON MY GUILT (we are only one year apart but I felt awful for liking him because he was the younger one and I didn't feel like he was 'like a brother' or anything like I did with my other friends who are younger) kinda half vent kinda not but this is mostly based off of what happened except a bit different trying to fit it into hucklerobby :/
Robby hates fathers day because he feels bad every time he is mistaken as Dennis's dad when they are in public together, brings up the fact that Dennis is younger and he still feels guilty because Dennis is literally half his age. Dennis always takes it in stride telling whoever asks that they are in a very loving relationship while holding Robbys hand and playing with his fingers until he gets out of his head.
When they get home they spend the night doing nothing crazy, just dining in and talking but before they go to bed Robby thinks about the time Dennis confessed.
Telling him he loves him and running away after, practically tripping over his own shoes and leaving Robby alone holding an umbrella he had offered to the other man because it was supposed to rain later and he was walking to the bus stop because Trinity wasn't on shift that day.
Robby had immediately ran inside to pull Jack aside from the case he had been working on, telling him Dennis confessed and pacing telling Jack that he was scared. Scared that he made himself seem better than he was to the younger man, that he had groomed him into thinking he was someone worth loving. Terrified that if he acted on it (cause he wanted to, god he wanted to) then it would ruin everything, ruin Dennis who was too bright and too happy to be stuck with a disappointment like him.
Jack had laughed in his face, saying he was stupid while patting his back. Telling him that the kid had been trailing him around like a puppy since his first day and the feeling was obviously mutual so why wouldn't he try?
'and if I ruin it?' Robby croaked, tears burning his eyes.
'then you fix it, and grovel until he understands that you love him more than anything.' Jack shrugged, patting his shoulder one final time before leaving Robby alone on the roof.
Robby had texted Dennis about an hour later, asking if he wanted to get coffee on Saturday.
And now holding Dennis in his arms, in his bed while Dennis talked about anything that crossed his sleepy mind, the guilt is gone replaced by overwhelming love.