People
Tidus' more important relationships are described in the Childhood and Love sections, but he does react with the others in his party. His story wouldn't have been what it was without them.
Auron - Auron is the beginning to Tidus' end. After Tidus' parents died Auron becomes a parent-like figure for Tidus, and someone he looks up to. Giving Tidus Jecht's weapon, Auron is the reason Tidus didn't die with Zanarkand and ended up in Spira. Auron also knew of Tidus' truth and fate and left it a secret from the group and Tidus until the end.
Wakka - Wakka is the brother Tidus never had, and Tidus ends up replacing, at least in fondness, the brother Wakka lost. The two become very close from almost the beginning because of their shared interest in Blitzball, and Wakka even asks him to join his team. Wakka is the one who introduced Tidus to the party, making his transition from famous Blitzball player to Guardian easier.
Lulu - I got the feeling that Lulu didn't really care for Tidus too much in the beginning. He resembled her deceased love, Wakka's brother Chap, and I wonder if her hostility was a result of the pain she felt when she looked at Tidus. Regardless of her feelings toward Tidus, she's the one he chose to teach him about Spira. Lulu was most against Tidus and Yuna falling for each other, but I think she began to respect him when she saw how much Yuna needed him, and even more so when he decided to sacrifice himself for the people of Spira.
Kimahri - Though Kimahri eventually comes to accept Tidus' presence in the party, he's much like Lulu in the beginning. He's overprotective of Yuna and doesn't want Tidus to have anything to do with her. He succumbs to Yuna's desires though, and becomes an asset to Tidus' journey.
Rikku - The thing that really surprised me was not how similar Rikku was to Tidus, but how close the two became. In the beginning Rikku knocked Tidus out and kidnapped him on her ship with her people. I thought for sure the two would become enemies, but I was wrong. I think they saw the weaknesses in each other and without saying, decided to bond. Rikku supported Tidus and listened to him talk about Zanarkand when no one else would. Heck, she even pretended to believe him, and she was very quick to offer him help, getting her people to take him to Luca. On the reverse side, when Rikku joined the party Tidus hid her identity as an Al Bhed from Wakka, who loathed them.
Poltergeist was created and is maintained by me, Todd, and is part of the Dragonzord Network. This shrine was made for fun and is entirely non-profit. It is made up of my own personal opinions and perception. Sadly, I don't own Tidus or Final Fantasy X. They are both property of Square-Enix. Please don't sue me.