Not much is known about the official origins of Obi-Wan Kenobi.
When he was young he became Master Qui-Gon Jinn's Padawan
and learned quickly and well. Though sometimes amazed at
Qui-Gon's apparent defiance of The Code and the Council,
he nevertheless greatly admired him.

He and Qui-Gon were sent on a mission to settle the conflict between
Naboo and the Trade Federation by peacefully meeting with the Viceroy
of the Federation. From the time he arrived on the droid control ship,
Obi-Wan had a bad feeling about the whole business, though Qui-Gon seemed
confident. When the Viceroy (ordered by Darth Sidious) sent battle and
destroyer droids to attack them, Obi-Wan's doubts were verified.
After seeing the immense droid army assembling, he and Qui-Gon split
up and stowed away on ships to try and warn the Naboo.

Along the way they met Jar-Jar Binks, a Gun-Gan, who brought
them to the hidden underwater Gun-Gan city. After getting a transport
through the planet's core, which Obi-Wan expertly piloted, they arrived
at Theed (Naboo's capital city) and from there saw the queen whom they
took with them to Coruscant. When passing the Trade Federation blockade,
their ship was damaged and they were forced to land on Tatooine, a remote
planet controlled by the Hutts. Obi-Wan stayed with the ship to protect
Queen Amidala (really Sabe in disguise) and tried to fix whatever he could.

Qui-Gon, after many adventures, acquired the parts they needed as well
as a slave boy (whom he freed) who was strong with the Force.
Obi-Wan was dubious about the boy, named Anakin Skywalker. They
soon arrived at Coruscant. When Queen Amidala decided to return
to Naboo, Obi-Wan and Qui-Gon accompanied her to discover the
identity of a mysterious sith who had attacked Qui-Gon at Tatooine.

Once there, with the help of the Gun-Gans, Obi-Wan, Qui-Gon and
Queen Amidala devised a plan to take back control of the planet.
While this plan was being put into action, however, the mysterious
sith (named Darth Maul) attacked them. Obi-Wan and Qui-Gon fought
valiently, but Qui-Gon was killed. Obi-Wan fought ferociously against
him and defeated Darth Maul, slicing him in half. Rushing to the side
of Qui-Gon, he held him as Qui gasped out "You must train the boy..."
and died. Obi-Wan promised and a large funeral was given in honour
of Qui-Gon Jinn. Obi-Wan at that time passed the trials to become a
jedi knight and took Anakin Skywalker as his Padawan...even against
the counsel of Master Yoda. He remains my favorite Padawan of all time.

Obi-Wan : Anakin : Luke : Humour : Allies : Contact