As the newer fish mature, they may pair with the older angel. Plenty of breeders split up & re-pair pairs once they determine their sex. My main concern would be that the remaining angel would have establised the tank as it's territory, and may show aggression towards newcomers.
It would be best to get at least 2 new angels, 3 would be better. Pull the older angel out temporarily, re-arrange the tank a little & add the new angels. After a few days add the older angel, see how they get along. If the older angel picks on one of the newer ones, you can return the youngster, eventually you will find a fish or 2 that are compatable. Given time, you may get a pair, or at least have a couple of fish that get along without aggression.
Tolak