Excerpt from my latest Sasstrology article (please leave comments on the Sasstrology site):
"Synastry overlays to the 5th House can lead to some sparkling, romantic fun. In a previous article, I described this as the house of self-expression. The 5th is also where your idea of capital R Romance lives. When someone’s planets fall here, they activate that romantic ideal and feed your creative fire. However, there’s not much to encourage a long-term relationship. Commitment takes work, and this is the house of play. There must be other, more binding contacts between two charts for a relationship to progress (if you want it to)."