Former Hills star Jenner and singer Lavigne have called time on their relationship after almost two years together, it was announced in January.
Entertainment magazine Life & Style reports that a source confirmed the break-up, saying it was down to opposing views on marriage.
Avril, 27, was previously married to Sum 41 singer Deryck Whibley and reportedly wanted to go down the aisle again - this time with 28-year-old Brody.
Could Jenner have been put off marriage by his step-sister Kim Kardashian's recent failed union?