My cat bites while "playing" with me?

my kitten is not aggressive he's just playing and purring while biting (he's almost 6 months and he is fixed)

but this is not my problem i can move my hand when he do this but after a month we will have another kitten (3months now but when i  have him he will be 4m) and i'm worried will the biting hurt him? Because it hurt me i can't take it for long

Kittens play rough with eachother.  The new kitten should be fine.  If you are worried just limit their play time as much as possible to only a few minutes at a time.  Just follow the proper introductions.  Young cats and kittens are USUALLY easier to introduce and accept eachother faster... Usually.  But you still need to follow proper proceedures.  They should be fine.  He shouldn't hurt the kitten. 

I agree with P3; read up on how to introduce cats and then supervise their play time in the beginning.  My two still wrestle and when one gets too rough; they let the other know.  I prefer to keep kittens kenneled when I cant supervise them.  (Young kittens)  When DH and I adopted Mooch and Noodles we bought a large wire crate that was big enough to put a small litter box in as well as food and water (at opposite ends) a bed and a few toys.  I was afraid they'd check out the fish tank a little too closely or something like that!  And the way the doors in our old place were; they could fit under them!