King Arthur, Gueneviere, Lancelot

This is actually a famous love triangle. It involves the noble King Arthur and his beautiful queen Gueneviere. She loves Arthur for his calmness but then also falls for Lancelot for his youth and energy. King Arthur and Lancelot are best friends. Lancelot and Gueneviere resist the attraction for a while but finally cave in, causing great sorrow for everybody.

This love triangle is often mentioned when a woman loves two men who are very good friends. The love of Gueneviere and Lancelot is sometimes brought to mind when a relationship *shouldn´t* be happening, and the couple tries to resist it, but are drawn together anyway.