R.R.
If the 14 month old understands "NO" and to not do it it in front of you, he's old enough for timeouts. This child proves that children know way more than we give them credit for ; ) Remove him from the situation to a place he can see what he is missing, a pack n play or sectioned off area. Explain why he's having a timeout, "We do not hit/bite/pull or we have a timeout" each and every time it happens, he'll eventually learn it's not worth it. Take him to your child after the timeout and say, "_____ is sorry he hit/bit/pulled you, right, _____?" Eventually he'll be able to say it on his own and have him do it. Do not turn your back on them unless they are separated, each in a pack n play or behind separate baby gates, I'd even separate them for play part of the time to avoid problems.
And do make his parents aware of what is going on and how you are dealing with it. Hopefully they will get on board so his discipline is consistent across the board, if not you'll need to decide it it's worth it to continue to watch him. I once watched a 4 year old who hit and kicked the other children when she thought i didn't see, literally fought me tooth and nail to not be in timeout and screamed at me when she was, her parents actually thought her behavior was cute :-/ So I had to say sorry, I can no longer watch her, which meant I lost her well-behaved sister as well. Truly wasn't worth it or fair to the other children.
Also, sit down and play with the kids on their level so they can see how to play nicely. They're toddlers, this is the perfect time to teach them. If the other child's behavior continues as it is you run the risk of your child starting to think it's OK. You'll be teaching your child it's not, and can also work on teaching how to stand up for oneself, because unfortunately, this is going to happen from time to time in years to come.