now I know that there's no way for me to respond to this without a bunch of fans of the modern adaptations ruining my inbox for the next week, but there's no evidence of Waluigi - or indeed Luigi - in any of the contemporary versions of the Mario-Wario sagas. The name "Wario" itself is a later invention, held to be a pun on warui that likely emerged after the adoption of Japanese scripts in the Koopa States.
The conflict between Mario and his "boyhood rival" was one over political influence on his home island and Mario's long absences - in particular his trip to Sarasaland. While later Sarasan sources would heavily reference Mario's brother, he is absent from both the preceding narrative and the unrest in Mario's homeland. The historical consensus is that the Sarasaland journey was one of Mario's earliest wanderings, with his brother attempting to manage affairs in his absence and proving unfit. The invention of a separate "Wario" character and its development into an explicit coup d'etat were later poetic creations, as is distancing of the "Wario" figure from the later depictions of Mario's brother as the more cowardly and reserved "Luigi".
(As an aside: "Mario Land" is a mistranslation. The original Mushroomer and Sarasan chronicles are better translated as "the land of Mario", without connotations of ownership. The modern scholastic consensus is that it refers to Yoshi's Island, where Mario and his brother spent their youth and later established a small manor, not, as commonly depicted, a "Mario Castle". The emphasis on Mario as king of "Mario Land" was a mostly successful political maneuver by the Yoshis to retain coequal status with the Mushroom Kingdom heartlands in the face of 18th-century expansionist pan-Mushroomism.)
The later emergence of "Waluigi" is an ironic recombination of two figures from the same historical source, and may have originated as a farce parodying the Mario stories. (The name "Waluigi" is also conflated with the early Norman figure Varr Yngwi, who is generally credited with the invention of tennis.)
