xD There's more to it and it's in the perfect ending xD

Ahh, I don't think they died, its never revealed. Tidus is part of the Fayth's memory of the night Zanarkand fell, but it never really says if the two are connected. I think that Tidus was supposed to die in the first SIN attack and Shuyin is actually later in the war, cause Lenne is a summoner at that point, Tidus has no knowledge of summoners or of a war when he gets to Spira. Shuyin is all bitter-like cause of the war... so I doubt they're connected life-wise.

My personal feeling is no and that's because I haven't seen any evidence to prove it besides the idea that they just look alike... and have the same final attacks.

PyroStatic might be able to say more he's palyed it like 6 times xD I haven't gottren to the Den of Woe but I know you find out more about Shuyin there, cause that's where he posessed Nooj.

I'm not much help eh? I have 10% left to get for the perfect ending so I can't be much help eh? lol