I have had this happen. It is not common, but happens and is no problem as long as all the babies, usually 4 at one time, are being fed by all 3 parents. If you seperate one of the hens and put her with her own rooster to pair with, things will get back to normal.
I have a male pigeon that is paired with 3 seperate hens feeds all 3 and at times he has 3 sets of babies at once. He has a nest for each hen and feeds all 3 sets of babies. if they r all close in age when they leave the nest he is bombarded by babies wanting fed all the time. The funny thing is I have several other males that have no mates because he takes all of them. He is working on getting yet another female to pair with him now and has been feeding her mateing her and they have picked a nest together. there was another hen of his but i gave her away cause Im afraid this is gonna kill him. His name is Rico Suave. All the babies do great usally hatch a few days apart and once they leave all the hens have new eggs again. Funny thing is altho all his hens look different some different breeds and none look like father almost all the babies look like Daddy when the r grown. I have had pigeons for years and have never experinced this til him. I had a dove one that had three mates but they all shared the same nest and hatched about 5 babies each time and altho chicks ranged in size a bit they always raised all of them but that was years ago.