Yes, they can. The number of the gang members in both gangs is not a major factor in the Kings of the City matching. Otherwise, gangs with few players would have a real problem finding opponents each day.

Please note that there a lot of gangs out there that have 25 players but only half of these players are active. The system can't predict which and how many players will choose to join the attack in each gang, so the numbers do not hinder the matching if the other factors do match.