Liam McShane

Liam McShane was the long-lost brother of Dorothy Gale "Ace" McShane.

Biography
Liam was four years younger than Dorothy. Shortly after his birth, their mother Audrey had an affair with their father's best friend. When their father learned of this he left Perivale, taking the infant Liam with him. Dorothy was only four years old at the time, so Audrey simply never told her about any of it and raised her as an only child.

In 1993 Liam's father had a heart attack, and finally admitted to Liam that he had a sister. Liam tracked down Audrey but she turned him away, telling him only that his sister had begun calling herself "Ace" and had disappeared years earlier, and giving him a photograph of her. Before Liam returned home with this information, his father had died.

Liam finally met Ace in 1997 in Ibiza, where he had gone with his friend Caitriona. He recognised Ace as his sister Dorothy from Audrey's photograph. Eventually Liam revealed who he was to Ace and told her everything, proving his claim by showing her a letter from their father. Ace, overwhelmed by how different her life could have been if not for her mother's lies, told Liam everything about herself and her travels with the Doctor in the TARDIS.

Ace initially decided she wanted nothing to do with Liam, having worked hard to sort her life out as she was she didn't feel there was any room for a brother in it. However, after Liam and Caitriona helped the Doctor and Ace foil the plans of "angels" Jude and Gabriel, Liam and Ace put aside their differences and spent several days catching up. When it came time to part ways, Liam elected to stay on Earth with Caitriona, knowing that he could never handle the kind of life Ace lived. Ace continued her adventures with the Doctor, with the new knowledge that she now had something to look forward to coming back to one day. (BFA: The Rapture)