D/S makes me think of Romeo and Juliet. Here are the reasons why :

1) Their parents "Hate" the other family.

2) They're about the same age as Romeo and Juliet

3) Danny is Sam's first love, so is Juliet and Romeo

4) Danny had "loved" someone else before  having some feelings towards Sam. So does Romeo, he "loved" someone named Rosaline.

That's all I can think of right now.