More than likely, what you are seeing is a juvenile swan and a juvenile goose that were told by the parents, leave their nesting area and find a mate and new habitat for yourselves.

Since these birds are probably last year's cygnets/goslings they are not ready to find a mate or begin nesting. So, they have made friends with each other until they do become mature for mating/nesting which should occur next year. The only other possibility would be a swan and goose that have lost their mates and are not interested in re-pairing and are happy to have a pal to roam the pond.

If they are raising their necks to each other and communicating, then they have accepted each other as a pond companion, but will not mate. The Regal Swan