Mute Swans allowing previous Cygnets/young to stay

We have a relatively new pair of swans at our local park pond {previous male died of bird flu}  This is the new pairs second lot of Cygnets just hatched.  The male has been incredibly aggressive and sadly our ducklings cant enter the pond as they are killed.  Their previous cygnets stayed well beyond the usual time period and two of the 5 were finally chased off the pond only in the last month or so {im assuming they were male?} but the adults have allowed the remaining 3 Young adult swans to stay which seems odd? everyone has said surely once the cygnets hatch they will be seen off but far from it. Infact the young swans have been up next to the nest only since the new babies have hatched. Is this rare? i cant find any information online of similar situations. Would they of kept them around as extra protectors?? its just so different to our old pair, who were much less aggressive during breeding {not killing the ducklings} and saw their young off after the normal time. im so curious 

Thanks 

  • In addition

    Today the 3 young swans that the adults have allowed to stay are now trying to kill the cygnets. They have killed 1 of 7. And have taken over the small island where the nest is forcing the adults and new cygnets off the island. I’m baffled as to how the adults are allowing this to happen. The Cob seems more concerned with killing tiny ducklings than chasing off these young that are a threat to their new brood
  • Last years cygnet's are still in our park too, but in the opposite end of the lake. For the first time yesterday I saw the adults go up to the cygnets end and there was a bit of aggro but nothing seems to have come of it.