Alex Campbell

Alex Campbell was the son of Susan Foreman and the great-grandson of the Doctor

Early life
The only biological child of Susan and David Campbell, Alex was born ten years after the events of The Dalek Invasion of Earth. Susan and David did not tell him about his true heritage, as they believed it would make it hard for him to live his life on Earth. (BFA: An Earthly Child).

Meeting with the Doctor
After the death of his father, Alex grew rebellious. He joined youth groups opposed to the new Earth Council. When he was seventeen he met his great-grandfather, who saved him from the Guldreasi and told him of his true origin. The Doctor wanted Alex to have an education on Gallifrey to fulfil his full academic potential. However Alex saw Earth as his home and decided to stay with his mother. (BFA: An Earthly Child)

Six months later, Alex had Christmas dinner in the TARDIS with his mother, the Doctor and Lucie Miller. After this, Alex took up travelling the world with Lucie. (BFA: Relative Dimensions)

During the Daleks' second attempt to conquer Earth, Alex fronted a resistance with Lucie and saved the Doctor from being blown up in a Dalek saucer. Alex was later killed by a Dalek while helping Lucie plant a bomb to destroy the Daleks. (BFA: Lucie Miller, To the Death)