You know, it's just something I always wondered.
So Auron basicallytraveled to Dream Zanarkand after dying basically by riding Sin.
In some of the flashbacks you see Auron with Tidus as a child, so obviously this occurs not very long afterJecht becomes Sin, but when Jechit isn't large enough to terrorize Spira
In almost every flashback with Jecht and Tidus, just shows how much a crappy father Jecht was. So with Auron fulfilling is obligation to watch over Tidus from his promise to Jecht, for 10 years no less.
This means not only Auron spent more time with Tidus then Jecht did, but was more or less a far better guardian (I mean this in the parental sense), then Jecht ever was.
It makes you wonder why Tidus isn't more influenced by Auron rather basically becoming Jecht junior. I mean this in the sense of becoming like someone you resent / hate.
Tidus spent years being emotionally abused by Jecht. In the end it's not that he wanted to become like his father, it's that he didn't want to be the person he perceived Jecht thought him to be.
Also, Auron is far too reserved as a person to become a father figure to Tidus.
In retrospect, while both Auron and Jecht had the right ideas they didn't execute them well at all.