The 'Dancing on the Ceiling' hitmaker has had his reservations over the couple's romance because at 21, the model is 15 years younger than the 'Flip It Like Disick' star - who has three children with former partner Kourtney Kardashian - and though he isn't "entirely on board" with the couple, he is resigned to the fact they are staying together.
She told E! News: "Scott and Sofia are still together and all is well for now. They spent Thanksgiving with Lionel Richie and they all flew together on his private jet for their holiday trip.
"Lionel has accepted their relationship but still isn't entirely 100 percent on board with Scott mostly because of the age difference and how young Sofia is."
And the 'Hello' hitmaker is making "more of an effort" with the 'Keeping Up With the Kardashians' star because, after two years together, he can see how happy Scott makes his daughter.
The insider added: "Lionel can see how happy Sofia is though so he is definitely making more of an effort with Scott.
"He is a really honest, up front kind of guy and feels like his father-daughter relationship with Sofia is more important than anything so he's trying to be there for Sofia and to be supportive of her despite his reservations about her relationship.
"They all had a really great holiday together though and progress is for sure being made between Lionel and Scott."
The 70-year-old singer has previously described Sofia and Scott's relationship as a "phase".
He said: "She's 19. When you're 19 you know everything. Is it going to be for life? I don't know. But for right now it's just a phase and I'm going to stand real still in the corner, get me a good drink and not make too much noise."