Arwen was the youngest child of Elrond and Celebrían. Her elder brothers were the twins Elladan and Elrohir. Aragorn and Arwen fell in love but Elrond had a strict condition that Aragorn must fulfill before he would consent to let his daughter marry a mortal. That was that Aragorn must be king of both Arnor and Gondor. This eventually came to pass and they married.