Help!!!!!

[Leesa]

I have a question and need advice!!! I have an 11 yr old cat Simon and a 6 yr old cat oliver. I recently got a kitten (not by choice he was orphaned) My 11 yr old accepted him pretty fast but oliver on the other hand is being a grouch!!!!!!!!!! there all 3 males. oliver and simon are fixed, the kitten of corse isnt yet!! but when Oliver goes after him i dont reallly want to yell at him but i am afraid hes gonna hurt him! (Oliver weighs about 18-19 lbs hes a good size cat) So 2 day i squirted water on him........Is there a better way to get him to stop, any suggestions???? Now hes really Mad!!!!!! HELP!!!!!!!!