Offer 12 cycles of prayer in the midnight of 11 and 12 Ramadan such that in each cycle recite Surah Al-Ikhlas once after Fatiha. Then after finishing all 12 cycles, recite durood shareef 100 times and present all the reward to the beloved messenger (Peace be upon him). Then through the intercession of our beloved Messenger (Peace be upon him), pray to Allah Almighty with humility, sincerity and humbleness for at least 15 minutes for getting a suitable match for your sister or daughter. By the Grace of Almighty, your wish would be granted before the next Ramadan.