When I think of Tidus, daddy issues come to mind. I almost forget he had a mother. Tidus spent the majority of his life with his mother, though, and although not much is known about her, examining her is important to understanding Tidus' character.
Tidus' mother appears in a couple of dreams and flashbacks. In each, Jecht is either present, or is being talked about. In the first, Tidus' mom asks Tidus if he really hates Jecht, and tells him that if Jecht dies, Tidus will never be able to tell him how much he hates him. In another, Tidus' mom is having a conversation with Jecht, and tells Tidus to hold on when Tidus calls to her. In that flashback, Jecht tells Tidus' mom to go to Tidus, because he'll cry if she doesn't.
I don't think that Tidus' mother was disinterested in him, or didn't love Tidus. I just think Jecht was her world, and when Jecht was home, he consumed her attention. Sadly, I think Jecht was more important to her than Tidus, but maybe only because Jecht left home a lot. Perhaps she wanted to cherish the short time she had with Jecht, knowing he'd eventually leave again and Tidus would still be around.
Tidus later tells Yuna that his mother is why he started hating his father.
Whenever my old man was around, my mother wouldn't even look at me. Maybe that's when I started to resent him, even hate him.
When Tidus was seven, his father disappeared, leaving his mother and him alone. Jecht of course went to Spira and was a guardian on Lord Braska's pilgrimage. Tidus and his mother believed Jecht was dead, though. After that, it's implied that Tidus' mother gave up her will to live. Tidus narrates that his mother died shortly after his father left. He compared her to a lovebird.
The old lady next door told me... when a lovebird dies, the one left behind... It just gives up living so it can join its mate. It was just like that.
Tidus accidentally called on his mother at the Farplane. He was confused that she showed up, and told Yuna that she was never sent. Yuna told Tidus that his mother must have accepted death while she was still alive, then.
That bothered Tidus, and he jumped to his mother's defense. Although she may not have been the best, Tidus clearly loved his mother. I don't think he blamed her for leaving him alone; I think he blamed his father for his mother's death.
Tidus' mother couldn't live without Jecht, and because Tidus was still around and needed her, in Tidus' eyes, it was Jecht's fault she died because he left her. That is incredibly sad.