Trio - Buffy the Vampire Slayer - was created in 2001.
In Buffy the Vampire Slayer she doesn't end up with anyone. However in the final Series of Angel she gets with the Immortal. Later, in the season eight comic of Buffy the Vampire Slayer, we find out that it is possibly one of the two alias that is publicly hooking up with the immortal, thereby nulifying the possibility that we actually see Buffy in this episode of Angel.
The first vampire slayer was a girl named Sineya (as far as I know, her name is only mentioned once on-screen, when Willow, Giles, and Xander invoked the Enjoining Spell at the end of Season 4).Unlike all subsequent Slayers, Sineya's power came from being bound directly to a shadow demon by a trio of shaman. Thus she was notably stronger and faster than other Slayers, but far less "human".(There is a graphic novel titled Tales of the Slayers, which details the origins of the First Slayer; the story is briefly told in an episode of the final season of Buffy as well.)
Jorma Kaukonen Trio Live was created in 2001.
The Art of The Trio was created in 1980.
Kegelstatt Trio was created in 1786.
Xyrion Trio was created in 2001.
Trio Mediæval was created in 1997.
The October Trio was created in 2004.
Trio Esperança was created in 1958.
The Second Trio was created in 1977.
Zimbo Trio was created in 1964.
Verdehr Trio was created in 1972.