Is this play?

I'm starting to wonder if my cats are really playing or not. My oldest (by a few months) is very much an alpha cat- this is his house, I just live in it (his name is Alcott). The youngest, London, is very shy around visitors but very affectionate with me.
Occasionally while playing I hear London give a hurt yelp, and Alcott normally doesn't stop roughhousing. Alcott pounces on London quite often- including while London was on the toilet while I was toilet training them (I wonder if thats why he has an aversion to using it). While petting London I've also felt several scabs on his skin.
I don't necessarily think of it as fighting, but is there anyway to make Alcott play a little more gentler? I don't want London to live in fear, but he's a sort of nervous cat to begin with. They were together in the same foster home-- London was given to me free with Alcott since they were supposedly friends (but from the way this agency operates, who knows).

I have the EXACT same problem! I wish I knew the answer. I can't wait to hear what some of the replies are.

I think that this is normal, it's what my cats do anyway They pounce on each other (though usually Thisbe, my older cat, starts it) and roll around on the ground. I hear yelps and growls and occasionally hissing but they don't seem to be mad. If I get in between them, they don't turn and attack me and when they break apart they just go back to playing. Occasionally I find scabs under Sinatra's chin, but he doesn't seem to mind them and they don't seem to be hurting him. I think it's from when they lay end to end and they bunny kick each other on the chin. I keep their nails trimmed and that seems to help.

If London wasn't such a nervous cat I'd be less concerned...it makes me worry that Alcott is what makes him nervous!

I may be stating the obvious, but...if you keep all their claws clipped short, you can minimize the damage. (I've tried SoftPaws, too, but applying them is even more difficult than doing the clipping, so I gave them up.)