Robert McGonagall Jr was the youngest child and second son of Muggle Robert McGonagall Snr and witch Isobel Ross. He revealed his magical ability at a young age. His mother and older sister Minerva worked together to teach him and his older brother, Malcolm, that they could not go around flaunting their magic. They also worked to hide the "accidents and embarrassments" that the two boys' magic sometimes caused from their father. Robert eventually fathered at least one child. His offspring would often visit his sister's home in Hogsmeade during her brief marriage between 1981 and 1984.