Auron was one of the guardians of Lord Braska in the past he had died during an assault on Yunalesca however he remained roaming about to fulfill the wish of his friend Jecht to help out his son Tidus from Sin which Jecht would soon transform to later on. Auron succesfully does this later on in the game and then Yuna sends his spirit onward.
Rikku does not have a last name.
Reno's last name is Sinclair
They never tell you his last name. The characters in Final Fantasy X are only given their first names.
Barret's last name is Wallace.
Tifa's last name is Lockhart.
AeriS' last name is Gainsborough.
Vincent's last name is Valentine.
Cid's last name is Highwind.
Yuffie's last name is Kisaragi.
There is no place in Final Fantasy X or X-2 that says he has a last name. In fact, no one seems too have one.
Strife is the last name of Cloud in Final Fantasy VII. The game was released for the PlayStation in 1997.
When the first one came out, it was the developer's expected last game, hence his 'final' fantasy. It turned out the game was a hit, and more were made, but they kept the name.