My grandmother passed away, and my father and I washed her. What is the ruling on that?

A man should not wash a woman if there are women available to wash her. Among women, the closest relatives should be prioritized for washing the deceased woman, then the next closest. If no women are available, then the closest male Mahrams should be prioritized, such as the father, grandfather, or son. It is not permissible for a paternal cousin to wash his female cousin because he is a non-Mahram (definition). It is permissible for a husband and wife to wash each other. If no one from the same gender, or no Mahram, or no spouse is available to wash the deceased, then tayammum (definition) should be performed.