The Robert Stewart he listed is a illegitimate son and half brother to Mary, Queen of Scotland. He has no line to the throne. This "family tree" is shite, written by an autist who wants to feel special. There's also no evidence that Robert Stewart was Jame's illegitimate son, it was just accepted. Given how many children Euphemia had he could have been anyone's kid.
There's also a list of children he and Lady Jean Kennedy had. The Jean he lists would be the one who would go on to marry Patrick Leslie. The moment he get's to James Murray it all falls apart. Margaret would have a son by the name of James Muirhead, he wouldn't have a daughter by the name of Zipporah Murray. His daughters were named Anne, Lillias, Margaret, and Elizabeth Muirhead. Bessie would give birth to Lillias and Anna and Grisel would give birth to Margaret and Elizabeth. The family tree at this point turns into bit of a family circle with the Hamilton family.