A source told Page Six: "Pete is 28 and Kim is 41 – they are just in very different places at the moment.
"Pete is totally spontaneous and impulsive and wants her to fly to New York, or wherever he is on a moment's notice. But Kim has four kids and it isn't that easy. She needs to focus on the kids."
The couple broke up after first being linked in October last year weeks after the reality star made her hosting debut on Saturday Night Live, where the pair shared a kiss during a sketch.
Davidson has been away for months filming his upcoming movie 'Wizards!' in Australia, where Kardashian visited him in July for a getaway in the Daintree Rainforest.
Their split comes after a separate source said the "long distance hasn't been easy for Kim".
Kardashian is still entangled in the legal details of her divorce from her third husband Kanye West, 45, with whom she shares children North, 9, Saint, 6, Chicago, 4, and three-year-old Psalm.
It was reported Kanye's fifth divorce lawyer has withdrawn from the long-running case.
Davidson's other celebrity girlfriends include Andie MacDowell's daughter Margaret Qualley, 27, and supermodel Cindy Crawford's daughter Kaia Gerber, 20, as well as Ariana Grande, 29, Kate Beckinsale, 49, and 27-year-old Phoebe Dynevor.
