Lenne & Shuyin
Lenne's lover is a man named Shuyin who lived in the same era as her. Shuin was a star blitzball player of Zanarkand. Though it is not specified how they met, it is most likely that it was due to their high social status that they probably encountered each other more than once.
Taken from what little information that is offered in the sequel, one can tell that Shuin and Lenne really loved each other. As Tidus was based off of Shuyin, it is possible that they both shared lively and idealistic personality traits. As we have seen in modern times, however, Shuyin had the capability to become a violent, malicious individual. Lenne, on the other hand, is gentler and is Shuin's voice of reason. She can instantly sedate him, both in the past and the present. This is how they compliment each other and without Lenne, we can see how a thousand years of separation brought about his insane fury.
They live up to the meaning of being two halves of a whole. Shuin is certainly no pushover, in fact, he's powerful and agile warrior who knows how to use a sword. While he is physically strong, he lacks in fortitude and sensibility. This is where Lenne completes the whole. Spiritually, she's strong and gives Shuyin the emotional strength to continue on. Even after his death, it was simply the memory of Lenne that drove him to survive a thousand years as a powerful spirit. Since Lenne was probably physically weak (since she specialized in magic roles), and was likely to die on the battlefield of a losing war, it gave Shuyin another method of defining himself. He's her lover, but also her protector. Her need for physical protection allows Shuin to feel needed.
Shuin's reckless behavior from his desire to protect Lenne was what brought about their downfall and their separation after death. Shuin's angry spirit wandered Spira searching for her while Lenne resided within the Songstress sphere, though that doesn't meant that their tale doesn't end there.