Being married to someone's maternal half-sister and a paternal half-sister at the same time
I have a maternal half-sister and a paternal half-sister, both were married to the same man and I am their guardian. Is this permissible?
It is permissible for them to marry the same man at the same time, as permissibility is the basic rule and there is no evidence supporting the opposite. As for being their guardian, it is permissible to be your paternal half-sister's guardian in concluding her marriage contract in the absence of anyone worthier than you. However, it is not permissible for you to be your maternal half-sister's Waliy (a legal guardian representing the bride) without legal authorization from one of her guardians, if any, or from the ruler if she has no suitable Waliy. (Part No. 18; Page No. 338) May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.