The Feast of the Holy Family was instituted as liturgical celebration of the Roman Catholic Church to venerate the Holy Family–Jesus, Saint Joseph and Blessed Mary–as a model for all Christian families. The feast was first introduced in 1893 by Pope Leo XIII and set on the Sunday after the Epiphany. However in 1969 it was moved to the first Sunday after Christmas to make it part of the Christmas season.

Sources:
Feast of the Holy Family (Britannica.com)
The Feast of the Holy Family(ChurchYear.net)