From what I was told by Gage is the best thing to do is get 2 females to one male and sell the 2nd female and they can form a pair by buying one male and one female but you have a better chance with the trio.
I agree 100% with getting like 5-6 smaller fish to form a bond for a breeding pair but I figured bigger fish and do the trio have a good chance to get a pair and at 4" they are able to breed when they want.
Mine aren't really aggressive at all towards each other I think it all depends on the fish it self you never know with cichlids they can be fine one day then next thing you know you a a serial killer in your tank