At first he deceived a stranger, called himself his son, and now he is stuck in his lie: his father accepts him for his son, seriously believes that his son and daughter have found the elder brother! Even the family heirloom, the family value was found to the "son" found!

So Busygin became part of the family, which he accidentally fell into: he just wanted to get warm, that's what he called a lost relative. And he himself did not notice how he became a native! And now it does not matter whether he really is blood or not - he is considered his own, and he loved this family too!