If he's wagging his rear slowly, circling him, lifting his chin or rumbling, it's dominance. He wants the other male to submit to him. Two guinea pigs need at least 9 feet of space, perhaps more, but as you said they have their space. Do they each have their own little home? It may be helpful to give the son a type of shelter he can go to.
Otherwise it may be best to repeater them, especially if the son is attacking the father, and the father is not retaliating.

Separate. Sorry about that!

I've only seen him lift his chin, but I thought he was just sniffing the air. I made sure they did, both have their own space though the son just keeps following the dad about. They have about that much space atm, but when they are able to go outside, they will have even more. I'm hoping it'll help settle them down.

I checked to see if the son had any marks on him, but he doesn't, so I'm assuming the dad isn't retaliating. If the son carries on though, I'll have to permanently separate them. Though having two pigs by themselves seems sad.

It does seem sad, I have two boys myself. Tucker keeps trying to dominate his brother, Coffee. He does the rumbles, chin lifts. But he's never bitten him. It is odd though, guinea pigs are such social animals, I've never heard of flat out attack another. I'd see what the bigger space can do for them, maybe get them a divider, so they can still be near each other, but the father is safe until you figure it out.

Yeah, females tend to be fine, males on the other hand are rather odd, i mean, brothers are supposed to be okay with each other, but the two brothers we had would fight >_<. We ended up having to put them in seperate hutches.