Zoë Castillo's father Gabriel is a mild-mannered bioneer who appears to be in his forties or fifties. He has a clear Oxonian accent (we know that the Castillos lived in London when Zoë was small) and is a contented 23rd century citizen whose job takes him all over the world. At the beginning of Dreamfall, Gabriel is preparing for a business trip to Bombay, possibly connected to a recent promotion, but he is slightly cagey about the details of his trip.
He is clearly used to just having himself and Zoë at home – Zoë's mother died when she was four and whether they were married or not is unknown. Helena Chang, another bioneer, mentions that she "knew a Castillo once. A long time ago," and says that Zoë looks very much like her father. Zoë's conversations with her imply that Chang is her biological mother, but as she makes no mention of Chang to her father, there is no way to gauge the likelihood of this from his reaction.
Gabriel is very protective of his daughter – it is possible this is somehow related to the circumstances of her birth. During the Collapse, when she was ten, he made her stay indoors. If Zoë tells him she intends to have a party while he's away, he asks her if there will be any boys or alcohol, and if she tries to leave the house in her underwear he says "I'm telling you right now, no daughter of mine is going out dressed like that." He calls Zoë on her mobile throughout her journey to check up on her, and liaises with Wonkers and the home server to see if she is all right.
When Gabriel is contacted by the EYE about his daughter (in the infamous 'Rain Conversation'), he warns Zoë to comply with their requests and not do anything stupid out of loyalty to Reza Temiz. Given his questions about Zoë’s party arrangements, it is possible that he did not entirely approve of Zoë's relationship with Reza. But when we see 'Reza' in Zoë's hospital room at the end of the game, Gabriel greets him warmly.
Despite this, he is also a supportive father who is concerned about Zoë – despite being busy on his trip, he offers to get her material from Bombay University to help her find a new purpose in life. When discussing his daughter's decision not to follow in her father's footsteps, he describes it as "breaking with tradition, in true Castillo fashion." This could indicate that Gabriel himself had rebelled against expectations in his choice of career… or 'rebelled' in other ways.Whatever their differences and the current strains on their family, Gabriel and Zoë remain close. When Zoë lies in a coma, Gabriel stays at her bedside throughout, powerless to help her.
Gabriel grew up in England, raised by his Argentine father and an English mother.