Aaron (Resolution)

Aaron Sinclair (TV: Resolution) was the son of Grace O'Brien. (TV: The Woman Who Fell to Earth) He was "around" nineteen-years-old when his son, Ryan Sinclair, was born. (TV: The Tsuranga Conundrum)

As Ryan explained to the Thirteenth Doctor, his father was notoriously unreliable. He failed to attend his mother's funeral. (TV: The Woman Who Fell to Earth)

After Grace's funeral, he sent a letter to Ryan apologising for not being there. He expressed a desire to reconnect with his son and offered to let Ryan live with him as he was "proper" family, unlike Grace's husband Graham. Ryan told Graham that he disliked his father's notion of "proper" family. (TV: Arachnids in the UK)

Ryan theorised that his father avoided him because he reminded him of Ryan's mother, whom he had loved. (TV: The Tsuranga Conundrum)

On 1 January 2019, Aaron arrived at Graham's home, where he met Yaz and the Doctor. He desired to make amends with Ryan for not being there, citing the New Year as a way to start fresh. He was surprised to find Ryan called Graham "gramps" but left with Ryan to a cafe all the same. After failing to sell his microwave oven to the waiter, Aaron tried to convince his son he had changed, asking Ryan what he could say to help. Ryan then lectured Aaron on failing him during his childhood. Later, Aaron returned Ryan to Graham only to stay to for a while as Ryan went away with the Doctor and Yasmin in the TARDIS.

While waiting for their return, Graham confronted Aaron about not coming to Grace's funeral, with the man confessing he did not come because he believed, by not going, he could pretend Grace was still alive. When the Doctor and the others returned, Aaron and Graham joined them in confronting the Dalek, Aaron using his microwave oven to help destroy the Dalek's casing. However, the Dalek clasped on to Aaron and used him as a bartering chip to force the Doctor and the others to take him to Skaro. However, the Doctor tricked the Dalek, sending it into a supernova and saving Aaron's life. Once returned home, Aaron said farewell to his son, finally making amends. (TV: Resolution)