There are only three reasons that eggs do not hatch. One is that there is an environmental cause such as too much heat, too much cold, drought or flooding. Any of these weather factors could cause the eggs to go bad.

Second, a young mother who is not keeping the eggs warm or does not sit on them for an adequate time. Obviously, this is not the case in your swan.

Third, the most probable cause of eggs not hatching is that they are infertile. There are two possibilities for infertile eggs. Are you absolutely sure that you have a male swan and not two females? Female swans will lay eggs, sit on them and obviously, they will not hatch. The other possibility is that your swans (male or female) are infertile due to a health problem which prevents them from producing a viable cygnet.

In all of these cases, there is little that can be done without disrupting the swans. If you separate the swans and try to re-mate them with another swan, they may become stressed. There are also no guarantees that they will accept the new mate and both swans could be seriously injured or killed from the ensuing fights. So, this is not a good resolution.

You could try to incubate the swan eggs, but this is going to be a major undertaking as previously discussed, humans have a hard time determining adequate heat and humidity to produce a viable cygnet. You will need a commercial type incubator to try and replicate the proper heat and humidity. Also, swan eggs have a greater propensity to rot in an incubator and may explode causing a very smelly mess. Finally, if cygnets are produced, you will never be able to teach the swans swan-like behavior such as bathing, preening, searching for food and protection against predators. They will become imprinted on humans and will never be able to fend for themselves or be released onto a lake or pond without constant human intervention. This means that the cygnets will lead a life in a pen which is no life. So, realistically, the resolution to your situation is not very promising. Just enjoy the swans and realize that you may never get cygnets from this pair. The Regal Swan