Whom?

For sisters

"If there comes to you one whose religious commitment and akhlaq (manners) pleases you, then marry (your female relative who is under your care) to him, for if you do not do that, there will be tribulation on earth and much corruption" {Sunan Al-Tirmidhi # 1084}

For brothers

"A woman may be married for four reasons; her wealth, her lineage, her beauty and her religious commitment. Choose the one who is religiously-committed, may your hands be rubbed with dust (i.e, may you prosper)." {Narrated by al-Bukhari (5090, Muslim (1466))}