It is possible, but highly unlikely that a new male would suddenly come in and help a female swan sit on eggs produced by another male. Bonding would need to occur for this to happen and we seriously doubt this has had time to take place.

Most likely, the male is your old male that has been so scared by Mr. Bully, he is not coming anywhere near you or anyone else, much less leave his small corner of the property which he was told in no uncertain terms to remain. It may take a few days/weeks until everyone's testosterone settles and each family goes to their separate areas of the pond, hopefully, never to cross paths. If the cygnets from one family were to cross this demilitarized zone, they could be killed by the other family's male parent. The Regal Swan