Birds of December - swans again

A few days after I first sighted the 3 Tundra Swans in the river at Imazu I found them at the fields to the north-west and another bird had joined them. They were in exactly the right spot as the 2 Tundra swans in 2011. 2 of these birds looked imature and I wonder now if they are the same swans and have become a family. Wouldn't that be nice.

コハクチョウ,  Tundra Swan