Here's my background. Sorry for the wait. Things have calmed down now IRL.
Grishnak is the offspring of a consensual orc and human relationship. His mother was the lone adult on a steading on the Savage Frontier; she had been widowed when her husband went missing on a trading trip. Grishnak's father was a lone wanderer who somehow befriended the woman and her family. Year after year he would return at the end of every summer with game and gifts. Some years he would winter with the family.
After a while the orc too went missing, but not before Grishnak was brought into the world. The boy inherited his father's wanderlust and decided when he grew up he would see every corner of Faerun. Of course, at the time he thought the world couldn't be much larger than the vale he grew up in!