Nalfein Do'Urden was initially elderboy of the Do'Urden House. He was considered a significant asset to the house as he was reknown as a powerful wizard. He was initially the oldest brother of Drizzt Do'Urden, and his death actually saves the life of infant Drizzt.
When the Do'Urden House initiated a raid on House DeVir, Malice Do'Urden went into labor along with baby Drizzt.. Along with bringing Drizzt into the world, she used the birth to initiate a weapon to invoke a powerful spell to destroy her enemies. At the same time, Nalfein Do'Urden was killed by his younger brother, Dinin Do'Urden.
Dinin betrayed Nalfein in order to attain the role of elderboy of the house himself and was successful. Drizzt was supposed to be sacraficed to Lolth after his birth as Malice had promised the third son of House Do'Urden to Lolth as a sacrafice. However, since Dinin succeeded in his assasination of Nalfein Do'Urden, Drizzt was no longer the third boy of House Do'Urden, but rather the second living son.