Are you sure both are male? We thought we had two girls - went to the vet to be speyed and turned out both were male. It's hard to tell when they are young. If they are male-male they will be aggressive, if they are male-female they will breed pretty soon.
It is difficult to bond unneutered rabbits, but especially uneutered males. Their hormones mean they will naturally be aggressive and competitive towards another male. I'm not saying it can't be done, but as your rabbits get a bit older they will be more aggressive, plus spray urine all over to mark territory, poop all over etc. It's natural behaviour for a maturing rabbit. The same with the humping - it's establishing dominance.
Unforunately two uneutered male rabbits can seriously injure each other. If the one being mounted gets really fed up, it is not unknown for them to attack the other's genitals. There has been a recent thread on here about a rabbit having it's penis bitten off by another rabbit.
Neutering willl sort out all these problems. It cost us £38 per rabbit - which is not cheap, but it's a lot cheaper than the vet bills would have been if we had left them together.
Are you sure they are only 9 weeks? Ours didn't start the aggressive behaviour until about 3 months. They were then neutered asap - which is about 4 months.
The best course is to keep them separated, have them neutered, then bond them properly a few weeks later. Neutering is generally thought to make rabbits calmer too, so they will hopefully be more friendly afterwards.