Does the ablution of the wife or daughter become void if she helps her sick husband or father who is unable to relieve himself or attend to his cleanliness?

It is not permissible for a daughter to assist her father in istinja' (washing after relieving oneself) or to see his 'awrah (private parts) as long as he has a wife who can do so. However, if there is a necessity for the daughter to undertake this, then there is no harm, and she will be rewarded for her piety towards her father. As for wudu' (ablution), it is invalidated by a person touching their own private parts or those of another, or touching the anus, whether their own or another's. Thus, if a woman who is assisting her husband with istinja' touches his private parts without a barrier, or touches his anus, her wudu' is invalidated thereby.