Is there a connection between the vow made by the father of the sister's husband—which has not been fulfilled for eight years—and the misfortunes befalling her sister's husband?

Whoever vows a vow of obedience, it is obligatory upon him to fulfill it, for the Prophet, peace and blessings be upon him, said: "Whoever vows to obey Allah, let him obey Him; and whoever vows to disobey Him, let him not disobey Him." And this father's vow is a vow of obedience that he must fulfill, and delay does not nullify it. As for the calamities befalling his son's house, they are not a consequence of his father's failure to fulfill the vow, for Allah Almighty says: {And no bearer of burdens will bear the burden of another.}