Welcome to the site, brother! Good to see you here! And thank you for entrusting us with your question.
That's great that you want to approach the sister for a marriage proposal. As our resident and smart IB member BilalKid said to you, you need to be able to get the father's contact details from the sister and then approach the issue in a respectful and humble manner in a face-to-face meeting.
You never indicated that the girl also has shown any interest in you; and therefore, you'll also have to discover whether the girl will be comfortable in having you ask her hand in marriage from her parents. She might have her own ideas of whom she wants to marry; and therefore, it is important you find that out because friendships do not always indicate a romantic bent from the female's side, and therefore you have to absolutely be sure that this is something she also would like and desires before you proceed.
In Islam, please know there is no racism
; however, some people are more culturally oriented than oriented in Islam which is evidenced with you saying that the father drinks alcohol and wants an Afghani man to marry her. Therefore, you might face opposition from her father simply on account of you not being an Afghani; so, you must approach the issue with the sensitivity it requires and basically gently and respectfully persuade her father that you will be able the best for his daughter because you will be able to be a good provider for her and care for her and that her happiness will be your top priority. He may consider you then as a prospect for his daughter and you need to make clear that you are asking his daughter's hand in marriage because you also respect him and the Afghani culture and you will act as a son to them once he allows you to marry his daughter. Basically, you need to win his heart and possibly also the mother's. Listen to them and be sensitive to their concerns.
However, any opposition you might face is all speculation at this point; you'll need to first approach and we can then In-sha-Allah (God-willing)
advise you based on that as situation unfolds and we know what you're really up against. Also, please make duas (supplications to God)
that Allah makes this process extremely easy for you and that if marrying this girl is in your best interests that her parents also agree and give you complete blessings. Also, first and foremost, try to find out if the girl even might consider you as a marital prospect.
Originally Posted by treborskar