third one's the charm?

Hello - I'm asking for some advice. Currently there are three cats in my house - two 1 yr old males (Harvey and Marty), and a male kitten (Foster) and we are having domestic troubles.

I have had Harvey and Marty since they were kittens and the two of them have gotten along wonderfully from the beginning; but about two weeks ago Harvey came down with an ear infection and started attacking Marty (with intent to hurt, this was not their usual play-fighting) everytime he tried to play with him. Understandably Harvey was in pain and didn't want to be bothered, but in the past two weeks he has been to the vet, was put on medication, and the infection has cleared up.

Then about a week ago I found a 5 week old kitten outside my house, took him to the vet where he was pronounced healthy, so he has been introduced to Harvey and Marty and joined the family. The introduction process went very smoothly - Marty took to Foster immediately and has been playing and sleeping with him since the first day. Harvey, on the other hand, resisted the newcomer. Again, he had been sick right before the introduction of the kitten, so I knew I would have to have patience with him. But within the past few days he too has started cuddling and playing with the kitten. However he is still attacking Marty like he did before his ear infection was treated, and poor Marty is very very confused as to why he can't play with his buddy anymore.

I wanted to believe Harvey was acting out because he was sick, but I'm not sure if that is the case anymore. Does anyone have any suggestions to restore harmony between the two of them? I would really appreciate any info you could give me - thank you!