Alice & Jasper
Alice foresaw Jasper finding her in a vision before he even knew he was looking for her. They met face-to-face in a diner located in Philadelphia, where she told him that she had been waiting a long time for his arrival. A little bewildered but intrigued with her knowing him, Jasper "ducked his head like a good southern gentleman" and answered, "I'm sorry, ma'am." She offered him her hand, a non-verbal question of whether or not he would like to go with her. He did indeed take her hand, as the sight of it brought him hope "for the first time in almost a century". During their companionship and travels, they fell in love. By 1950, they found Carlisle with more assistance from her visions and have been part of his coven ever since.

Alice and Jasper have been together since the 1950s, but are not as flamboyant with their relationship as their "siblings", Rosalie and Emmett, although they are stated to be soul mates and have been legally married. Jasper and Alice understand each other and are very protective. Jasper will do anything to keep Alice safe. Alice will also not let him get hurt, and keeps him from going with her to Italy during New Moon for his own safety.

Source: Wikipedia