What is the ruling of Islamic law regarding a young man continuing to communicate with the sister of a girl he is interested in marrying, after her mother's repeated and unjustified refusal, and with the help of the sister who communicates with the young man without her family's knowledge or even her sister's, knowing that the sister is aware that her action goes against her conscience, all for the purpose of completing the marriage?

There is no harm in a sister speaking to a young man if she is safe from temptation and the conversation is limited to what is necessary, without softening her speech. It is preferable that this occur through the woman's mahrams.

The mother does not have guardianship over marrying off her daughter; rather, guardianship belongs to the male relatives (Asabat), and the most entitled among them are the father, then the grandfather, then the son, then the brothers.

If the young man is suitable and the girl desires him, her family does not have the right to prevent her, and she may refer the matter to the judge to marry her off.

It is advised that the young man propose to the girl's legal guardian. If the mother refuses, some relatives should intervene to persuade her. If she insists on refusing, there is no impediment to marrying off the girl despite her mother's objection, while still upholding the duty to honor and be good to the mother.