2 Male Kittens Fighting

Question
We adopted 2 male litter-mates from the SPCA on October 16th.  They are about 3 1/2 months old right now.  When we brought them home, one was already getting a "cold" where he was sneezing and sniffling.  The other kitten picked it up 2 days later.  We took them to the vet and got medicine that they have been on for about a week and they are almost back to 100%.  In all of this time, they have been really nice to each other and play with toys with each other, but for the last couple of days (about 4 days) they fight almost CONSTANTLY.  I thought at first that it was play fighting, but now I am not so sure.  They start off by chasing each other down and then get on top of each other, one on his back, the other on top of him and claw/bite/hiss/growl for long periods of time.  I haven't seen any blood yet, but it just seems REALLY rough.  That, and the fact that they are hissing and growling at each other.  We always break it up after about 2 minutes or so because I don't want them hurting each other.  I just don't know if this is normal or of they are actually fighting.  And if they are, what should I do?  Any help is appreciated!

Answer
Littermates play extremely rough with each other. If you are really concerned contact the SPCA to confirm that these little ones are indeed littermates. I wouldn't be too concerned just based on the fact that kitten play fight with each other normally, they will growl, hiss, bite, and generally put on a pretty good performance. If you aren't seeing injuries you may want to just wait and see. If you are still concerned you could take them to the vet just to confirm that there are no injuries. Hopefully this explanation helps. Please do not hesitate to contact me with further questions.