White Wolf is Hunter, a man whose parents died in a plane crash in the African nation of Wakanda when he was a small child. As a result, he was adopted by the nation's king, T'Chaka (Black Panther's father) before T'Challa was born and grew up as T'Challa's adopted brother. After T'Challa was born, Hunter knew that he wouldn't be the one to replace T'Chaka on the throne. Feeling somewhat hard done by and cheated, he developed a deep jealousy for his adopted brother. In an attempt to upstage T'Challa, Hunter aimed to be the best Wakanadan citizen that he could possibly be. It was this that led to T'Chaka appointing Hunter as leader of the Wakanda's secret police - the Hatut Zeraze. From that point, he became known as the White Wolf. When T'Challa became king following T'Chaka's assassination, he disbanded the Hatut Zeraze because of their brutality. Hunter, with his men, left Wakanda and became mercenaries. Though resentful of this effective exile, Hunter still loved Wakanda and thus tempered his resentment of T'Challa to aid his country when needed. Having White Wolf in a movie would be somewhat like the Thor and Loki relationship in the first Thor movie - though with White Wolf as less of an outright villain and more of a rival of the titular character. Seeing Black Panther and his Father trying to get through to White Wolf would make for a very interesting plot and a somewhat different kind of superhero movie to anything we've seen in the Marvel Cinematic Universe before.
