Allow me to define "holy," for our immediate purpose, as the state of being Christ centered.
The holy family is of course Jesus, Mary and Joseph. Grandparents, uncles, aunts and cousins are not included in this traditional grouping because what we are celebrating is a logical extension of Christmas.
We are paying respect to the immediate context within which the Incarnation took place... a context upon which God placed his seal of approval in a unique way. That context is a family... a husband, a wife and a child or children.
That having been said, I think that we would be overreaching were we to attempt to make a case for The Holy Family being a template for Christian families.
Surely it would be ridiculous to suggest that children should emulate the child Jesus. After all, we know so little about his childhood aside from his disappearing for a day or two while his parents, frantic with worry, searched for him!
And if I were to suggest that you mothers should live your daily lives as did Mary, you might in turn suggest to me that unlike Mary you were not born free from original sin. As for Joseph, the dear manís role and vocation was unique to say the least.
So, the feast of The Holy Family, like Christmas ought to be placed in proper focus.
I leave you with a question: In the light of all of the above, what should distinguish your family from that of a modern secular family?