Hello Erin…..you need to take him to the Vet. Urinating suddenly like this could be sign there something wrong…kidneys, crystals a bladder infection…all sorts of things. Take a urine sample with you if you possibly can, it will help the Vet pinpoint the problem.
Hope he recovers soon!
Male kittens tend to play more rough than girls. Sometimes cuts happen and when they otherwise undertsand each other well and get along, if they are playing and enjoying each other I would just let them be.
Maybe trim their nails and offer things to sratch on.