Chomir Ali, 44, his sons Mohammed Mujibar Rahman, 19, and Mamnoor Rahman, 16, will now be sentenced to life imprisonment for the murder of Arash Ghorbani-Zarin, a 19-year-old university student, on November 20 last year.
Mr Ghorbani-Zarin, an Iranian Muslim studying engineering at Oxford Brookes University, had been stabbed 46 times when he was found dead in his car in Rosehill, Oxford.
A jury at Oxford Crown Court took four-and-a-half days to reach a verdict. Mr Justice Gross adjourned sentencing for reports on Mamnoor.
Mr Ghorbani-Zarin had been dating Ali's daughter Manna Begum, who was promised to someone else by her father, since 2003. She fell pregnant soon after.
Mr Justice Gross said the Western-style relationship caused a "battle of wills" in Miss Begum's family, as she refused to conform.
In a statement, the Ghorbani-Zarin family said: "This verdict gives us some comfort that justice has been done but it does not bring him back."Reuse content