And the 20-year-old confessed to feeling a twinge of jealousy at Mako's achievements while revealing the Wallabies have not been the only ones on the receiving end of the prop's competitive spirit recently.
"I was a bit envious when I watched Mako in the summer," said Billy, who is a number eight.
"He did well and I'm very proud of him, but obviously I'd have loved to have been the centre of attention in my family.
"Mako always seems to do things before me. I'm always playing catch up. Maybe I'll be the first of us to get a girlfriend!
"We live together and I find myself being a bit of a maid. Not because I'm being forced to, but I like to be clean.
"I don't fear him, I respect him because he's the elder brother and what he says goes."