Mounting is entirely normal. There isn’t anything concerning here - it’s normal dominance. Don’t separate them for normal dominance. You only separate if there is a full on fight and clear break in bond, or if there are signs of bullying.
As the son gets older and hits his teens the dominance is going to occur/increase. Particularly as the dad is also a teen and at six months he is also experiencing his highest hormone output.
How big is their cage? Two boars need a cage measuring 180cm x 60cm. If your cage is smaller than that, then yes they will need more space. Should you need to increase their cage size then you need to do it carefully as changing the cage will create a change in territories which will create more dominance.
Boars do need two of everything though. You must also ensure you don’t have any enclosed hideys - all hideys must have two exits so no piggy can get cornered by the other piggy inside one
Please read the guides below for information.
A Comprehensive Guide to Guinea Pig Boars
Dominance Behaviours In Guinea Pigs
Boars: Teenage, Bullying, Fighting, Fall-outs And What Next?
Bonds In Trouble
