Tristan and Isolde
This tale belongs to the Celtic and Irish Mythology.
The story tells how Tristan and Isolde by mistake drink a love potion intended for Isolde and her fiance, the King Mark, which triggered the tragedy. They are separated, Tristan goes to France and get married, but he is still in love with Isolde. In the end, he falls mortally wounded and call her.
Isolde comes to his call, but the jealous wife makes him believe that not, so Tristan dies disconsolate. When Isolde comes, she dies too. Both are buried together, and in their graves grow two trees with branches intertwined forever.