Canada Geese

For many years we had a pair of Canada geese return to mate. They were quite happy, and we never saw any other geese before, during or after their time. 4 years ago,one of the adults died, and the remaining adult returned to wherever it came from and returned a few days later with another mate. Several more adult geese appeared after this. They eventually left after a couple of weeks of vocal arguing! Now we always have these visitors, but are eventually left with three adults.  I am assuming there is one male as there is now 2 nests. One of the females lays eggs every year, but it appears these are sterile as they never hatch. The other pair do mate and raise a family. The three remain together, but are fighting continuously, 24/7, and is a very noisy period. My question is, is this normal behaviour, and why does the other female not find herself a mate?