Convicts are pairing fish, not colony breeders... Therefore a male and female will pair off and then see any other Convict in the tank as a threat to their pair/babies... another pair may stand up to them okay but any unpaired fish are in trouble... therefore you should have an even number of males and females...
When they are younger/smaller you could keep two pair, maybe three... when they are actual adults you could keep one pair, maybe two...
I would suggest giving yourself some diversity though... such one pair of two different species of fish...