Scott Disick and Sofia Richie. Picture: Instagram

Sofia Richie has been spotted on her first public appearance alongside two of Scott Disick's three children.

The 19-year-old daughter of music legend Lionel Richie has been romancing the reality star for several months, and over the weekend, they seemingly took their relationship to the next level, as the pair were spotted heading to dinner with two of Scott's three children.

Sofia, Scott, eight-year-old Mason and five-year-old Penelope - whom Scott has with his former partner Kourtney Kardashian - were seen by an eyewitness heading into Nobu Malibu on Friday at around 6:30pm, and are said to have left at around 8:15pm.

According to E! News, the group - which did not include Scott and Kourtney's youngest son Reign, three - are said to have sat at a table outside and Scott and Sofia sat on opposite sides of the table.

The insider also told the publication that "everyone was interacting and looking happy during the meal", and claimed Sofia "seemed comfortable with Scott's kids".

Sofia's blossoming romance with the 34-year-old 'Keeping Up with the Kardashians' star comes as sources previously stated the young star has been "great" at keeping Scott - who previously battled substance abuse for several years - on the straight and narrow.

A source said: "She's been great for him. She's made a big impact on his life and hasn't partied at all since they met. They've been travelling together to Mexico, New York and Venice and just hanging out. His friends adore her and nobody notices the age difference. She is very mature, she grew up in Hollywood and has always been in older situations. They seem really happy."

However, not everyone is supportive of their relationship - which began in May last year - as Sofia's father Lionel is believed to be concerned that Scott's "playboy ways" could mean heartbreak for his daughter in the future.

A source shared: "He thinks Scott is the worst person she could ever see and that he raised her better than that. 

"He thinks she should have more respect for herself as a young woman. Lionel knows Scott's playboy ways and he doesn't want to see his daughter get hurt."