Lancelot is a gargoyle of the Manhattan Clan.
Lancelot will hatch in the Manhattan Clan's rookery in 2058. Though the clan may or may not be aware of it, he is in fact the youngest of Broadway and Angela's three biological children, and biological brother to Artus and Gwenyvere. Little else is known of Lancelot.
Almost nothing is known about what Lancelot will look like, though Greg Weisman has hinted that he may resemble Goliath to some degree.
Real World Background
Lancelot is named after Sir Lancelot du Lac, King Arthur Pendragon's best knight and - unfortunately - the lover of Queen Guinevere; it was their love affair that helped destroy Arthur's kingdom. (According to Greg Weisman, Lancelot and Guinevere's affair did indeed occur in the Gargoyles Universe).  His name, together with that of Artus and Gwynevere, is a sign that whoever named them had a strong interest in the Arthurian legend.