Unknown Father of Robert de Brus - Rainier d'Brus?

According to some research... There was a an individual named "Rainer Brus or D'Brus" that was Norman-French. He was a Knight that joined the likes of Kt. Robert Curthose in The Early Crusades. It has been strongly suggested that "The Brus Family Line" goes through him? Anyone having any additional verification ... is welcome to contribute and/or discuss this.

Thanks;

Al