There's some overleap between what we learn from/about Gillian and Mike and their respective partners, but Lena's brother has been a complete no-show so far, so him turning out to be Gillian's guy would be a pure ass pull, compared to the alternative. So, while not completely impossible, makes it pretty unlikely.I know that Mike was the guy who Gillam cheated with is a popular theory but my frist timing playing my first thought was Lena's brother.