In order to be 100% sure, you would need to conduct DNA Sequencing or wait until the birds mate and lay their first eggs. The two birds that the Male is chasing are either juvenile swans or the mother swan and a juvenile. Juveniles are the same species but their bills have not turned completely reddish/orange. This usually occurs around 1 year of age. In any case, once the cygnets become juveniles and turn white in color, the parents kick them from the nest and the habitat so that is the behavior you are observing. The male is probably chasing the juvenile and not the female (DO YOU KNOW IF THE MALE SWAN HAS A MATE AND IF SHE IS ONE OF THE TWO SMALLER BIRDS?)

The adult male swan looks like the one with the reddish orange beak (known as a royal mute) and the adult female with the lighter colored orange beak (polish mute-leucistic coloring) are both mute swans. Again, we can't be 100% sure without either DNA Sequencing or sexing the birds and not having more information as to whether two of these swans are adult mates. The Regal Swan