What is Islam's ruling on my mother or one of my sisters leading me in prayer?

There is no harm for a woman to pray in the presence of her husband, or one of her mahrams, or a non-mahram man, as long as she is covering what she is obligated to cover in prayer. Her prayer is valid. However, it is preferable for her to pray in a place that conceals her from the sight of men, due to the Prophet's (peace and blessings be upon him) saying: "A woman's prayer in her house is better than her prayer in her courtyard, and her prayer in her private chamber is better than her prayer in her house."