There is no physical connection of the child with any other person including the father or grandparents.
So what role can the father play ? Father, for sure, participates in the process of conception.
Once pregnant, the mother carries the embryo and foetus in the womb. She connects with the child physically, through the umbilical cord and placenta.
It is well known that the mother is the channel for physical movement of food/ nutrients and waste disposal for the child.