All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.
Scholars cited that it is obligatory upon the children who have the financial capability to help their indigent father who seeks chastity to marry. Thus, you have to respond to your father's request and marry him off. His cancellation of the first wedding does not entitle you to turn down his request the second time. Maybe he had some illness or a sudden disinclination for marriage, which was temporary. Medically speaking, past and contemporary researches show that men are capable of fulfilling their sexual desire and its implications even after the age of a hundred.
Allaah Knows best.