Things are getting more serious between the couple, who were first linked in November.
"Amelia and Scott are doing well," a source tells ET of the 19-year-old model and the 37-year-old businessman. "Amelia is mature for her age, and Scott and her [get] along great and things are easy."
The romance is even more meaningful because it marks Amelia's "first serious boyfriend."
"She's really into him," the source adds. "She likes to be cute with him and definitely has a big 'crush' on him."
The couple has plans to spend the summer together in the Hamptons.
Another source previously told ET in March that the couple was considering moving to Miami, Florida, together.
"Amelia is planning on moving in with him. Scott was lonely when he and Sofia [Richie] broke up, which is one of the reasons he and Amelia got together so quickly. They've been getting a bit more serious for now. Scott has been having a good time with Amelia," the source said at the time.
"Getting engaged and married one day has definitely been a topic of conversation between Kourtney and Travis," another source recently told ET. "Travis would absolutely love to tie the knot with Kourtney, but Kourtney hasn't been sure that's the step she wants to take in their relationship right now. She is extraordinarily happy and doesn't feel the need or want the pressure of getting married."