Imagine your dad grooming you to become a soldier so that at 17 you have to go gather civilians to be raped and killed while he gets a sunbathe. He also only came to your location to touch butt with Roger and not to save or help you.
Tells me that Garp and Dragon doesn't have a close relationship.
Or Garp was a horrible irresponsive dad during his prime, doesn't really care what his son is doing, whether he's in danger or not....
For some reason Oda's making them apart like there's a barrier between them.
Won't be surprised if we don't see any interaction throughout GV when both are at the same island really close to each other.
Young Garp has kinda cold personality, eg. during the first interaction with Kuzan in the fb. He was hard to connect during this age.....
Maybe he change for the better when he gets older.