This is slightly different,but still canon.

After Jack Frost's death caused by the ice breaking in a frozen river,passed years and years till the Man in the moon had decided to make him a guardian.

Unfortunately,Pitch found Jack first and made him join him forcefully.Jack has a mark on his right eye,meaning that he's connected to Pitch.

Also,Jack hasn't met the guardians yet,so nobody knows him either.

One day,Pitch sent Jack to spy on the guardians and he went to the place where the guardians were.

(You're Jack Frost.)