The great Godden / Meg Rosoff.

Everyone talks about falling in love like it's the most miraculous, life-changing thing in the world. Something happens, they say, and you know . That's what happened when I met Kit Godden. I looked into his eyes and I knew. Only everyone else knew too. Everyone else felt exactly the same way. This is the story of one family, one dreamy summer - the summer when everything changes. In a holiday house by the sea, our watchful narrator sees everything, including many things they shouldn't, as their brother and sisters, parents and older cousins fill hot days with wine and games and planning a wedding. Enter two brothers - irresistible, charming, languidly sexy Kit and surly, silent Hugo. Suddenly there's a serpent in this paradise - and the consequences will be devastating.