The pair went Instagram official over the weekend.
"Scott and Amelia are having a blast together. They've been going out with friends, spending time together and overall just having a really good time," the source says. "They're still not super serious and are just taking things day by day and keeping things light and fun."
"Amelia is young and doesn’t want or need a crazy commitment and Scott likes that things are low key and easy with her," the source adds of 19-year-old Hamlin and 37-year-old Disick.
The pair -- who went Instagram official on Saturday -- spent Valentine's Day together in Miami. Disick's ex, Kourtney Kardashian, seemingly spent the holiday with her new boyfriend, Travis Barker.
"Kourtney is doing just fine and doesn't have romantic feelings towards Scott anymore. She’s OK with Scott and Amelia’s relationship as long as he continues to prioritize their kids and be a good dad," ET's source shares.
As for Disick's other ex, Sofia Richie, the source says she's "happy to be out of her relationship with Scott and is focusing on herself, moving on and meeting new people."
See more on Disick in the video below.