On his father's side, Keynes is of English descent, and is the grandson of physiologist Richard Keynes, the nephew of two Cambridge professors, the historian Simon Keynes, and the neuroscientist Roger Keynes, the cousin of Catholic writer and apologist Laura Keynes, His maternal grandparents were Furugh Afnan and Cecil Fadlo Hourani, who was an advisor to the late Tunisian president Habib Bourguiba.
The Hourani family were immigrants to Manchester from Marjeyoun in southern Lebanon.
There he wrote as a film critic for the review section of The Citizen, the City of London School weekly school newspaper.
He sat his GCSEs in May and June 2008 and started Sixth Form and his first year of his A-level studies the following September.
He studied biology, chemistry, maths, further maths and history at A-level.
In October 2010, he began his degree in Arabic and Middle Eastern History at Pembroke College, Cambridge.
He and his family have visited Marjeyoun since he was a child.
When he later had to run in the same scene, he did so while on pain medication and worried it was noticeable.