Sister insists on marrying man she had relationship with
13-11-2017 | IslamWeb
Question:
Assalaamu alaykum. My sister is going to marry someone whom she has had a relationship with for a while (it was not a sexual relationship, she chatted with this person on social media for a while and perhaps even on the phone and in person; I do not know how far the relationship went, but at least it was on social media). The man prays, and I am told that he is a decent person, but I am not comfortable with him because of the relationship. My father wants me to be a witness to a signing for something called 'Milcha' (period of engagement, it is a Qatari term). My sister, in her intense desire to get married, harassed my father like mad and even bought a house for herself. My father worried that she would marry without his consent and maybe bring embarrassment to our family so he consented, but only as choosing a lesser evil. We have all spoken to my sister to tell her that what she is doing is wrong; even her friends do not stand by her, and she has cut the ties of friendship with them. She would not listen to us and acted in a completely offensive manner for maybe over a year, refusing to back down. Her relationship with this man started in a completely wrong way, and in order to get married, she made my father suffer psychologically, and he (my father) is not a young man. My father, having given up, has told me to be a witness to this signing (he does not want to be a witness to it), but I will only accept if it is halal. If I completely refuse this task, like I want to, my father will be upset and will be a witness himself, so I will only accept to be a witness if it is not haram for me to do so. Given the above, and given that my father has asked me to bear witness, is it permissible for me to be a witness?
Answer:
All perfect praise be to Allah, the Lord of the worlds. I testify that there is none worthy of worship except Allah and that Muhammad, sallallahu ʻalayhi wa sallam, is His slave and Messenger.
There is no doubt that a love affair outside of marriage is prohibited in Islamic Shariah. Rather, it is one of the practices of the Jaahiliyyah (pre-Islamic period of ignorance) which Islam abolished. Allah, the Exalted, says (what means): {(They should be) chaste, neither of those who commit unlawful intercourse randomly nor those who take (secret) lovers.} [Quran 4:25] Hence, it is incumbent on this young man and woman to repent to Allah of their illegitimate relationship.
As for her marriage to this young man, if his religiosity and manners are acceptable in general, meaning that he observes the religious obligations, especially the prayer, and avoids major sins, then there is no harm in marrying her off to him, especially given that she is emotionally attached to him and that there is no religious impediment to their marriage. Ibn ʻAbbaas, may Allah be pleased with him, narrated that the Prophet, sallallahu ʻalayhi wa sallam, said, “There is nothing like marriage for two people in love.” [Ibn Maajah]
It is permissible for you to be your sister's Wali (legal guardian) in this marriage contract if your father delegates you to do so, or to be a witness to the marriage. For more information, please refer to fatwa 83629 about the conditions for the validity of the marriage contract in Islam.
We would like to remind the girl's father that he shall be held accountable before Allah regarding her; he has to do whatever preserves her religiosity and honor. Allah, the Exalted, says (what means): {O you who have believed, protect yourselves and your families from a Fire whose fuel is people and stones...} [Quran 66:6]
As-Saʻdi 
said in his Tafseer (Quran exegesis):
“It means: O parents, your children are trusts deposited with you, and Allah has enjoined you to take care of them. You must strive to preserve their religious and worldly interests; you should teach, discipline, and protect them from corruption and evils. You should command them to obey Allah and adhere to Taqwa (piety and mindfulness of Allah). Allah, the Exalted, says (what means): {O you who have believed, protect yourselves and your families from a Fire whose fuel is people and stones.} [Quran 66:6] Children are entrusted to the parents; the parents either honor the trust or they neglect it and accordingly incur the relevant warning and punishment upon themselves.”
Allah knows best.