He is one of the sons of an unknown duck and Della Duck, who is the sister of Donald Duck and also the niece of Scrooge McDuck. Louie and his brothers, Huey and Deweyare either taken care of by Scrooge or Donald, depending on if Donald is in the navy or not.
Louie and his brothers were created by Ted Osborne and Al Taliaferro in 1938. Their first Disney animated appearance was in the 1938 short called "Donald's Nephews", where the three annoy Donald with their shenanigans.
They have also been shown in several shows including Duck Tales, where they fought such forces as Magica De Spell, Ma Beagle and several other antagonists (though they faced Magica earlier in the comics).
Interestingly enough, on several covers of Donald Duck Adventures, Louie's green shirt was replayed by a yellow one (while his other brothers continued to have their red and blue shirts).
This character has not really evolved too much from his first appearance. However, he and his brothers have gotten a little more obedient to their uncle and great uncle. They have even joined the junior woodchucks to help the earth.
When Scrooge makes a bet with John D. Rockerduck, he has to return several of the artifacts he has collected on his adventures (some of which Louie and his brothers collected).
Louie was one of the people who helped Scrooge bring the candy-striped ruby back to the island of Rippan Taro. However, who is lying in wait of them? find out in Duck Tales!