Scott Disick and Sofia Richie "bicker" at times but "always end up fine".
The 'Keeping Up With The Kardashians' star is so "comfortable" with the model that they make up pretty quickly after arguing with one another as they would "rather be together than apart".
A source told E! News: "They bicker at times but things are ok with them. They make empty threats that it's over and then they get back together. They are comfortable together, so it's easy to say things that you don't mean. They have drama but always end up fine. They spend a lot of time together and can sometimes push each other's buttons. Sofia will take her stuff and leave for a day or two. They know they would rather be together than apart."
Meanwhile, it was previously claimed that Scott and Sofia are "so committed to one another".
A source said of the couple: "Right now, Scott and Sofia aren't thinking about marriage or getting engaged and it's not a big topic of conversation. They are so committed to one another and neither of them are going anywhere. Scott has done a complete 180 from when he was younger and with Kourtney, and has grown up a lot."
The reality star - who has Mason, 10, Penelope, seven, and Reign, five, with his ex-girlfriend Kourtney Kardashian - is also looking to form a "close bond" with Sofia's famous father Lionel Richie, because he "recognises the importance" of family.
A separate source added: "Since Scott is a father himself, he recognises the importance of a close bond with his children and would never want to harm the relationship between Lionel and Sofia, especially because Scott's parents have both passed away. He values family above all else and will always look to build a bond with Sofia and her family, and would never want to detract from it."