Am I obligated to maintain ties of kinship with my "gay" father and his husband, knowing his actions and not knowing of his repentance, and would I be considered sinful if I cut off my ties with them?

It is the right of the father upon his child to be connected with him and to be dutiful to him, even if he is disobedient. This is based on the Almighty’s saying: "But if they endeavor to make you associate with Me that of which you have no knowledge, do not obey them, but accompany them in [this] world with appropriate kindness." Therefore, severing ties with one's father is a grave sin with an expedited punishment. Connect with your father through visits, calls, and inquiries. Give him from your wealth if you are able, and invite him to the truth, advising him gently. If your father owns the house, it is not permissible to force him to leave. However, if he leaves by his own choice, there is no harm.