What’s yoshi in Mario? 
How’s bowser a turtle? 
Is Mario in the games italiancuckerlet from Brooklyn? 
Is peach hooman? 
How’s Luigi different in games than Mario? 
Why it called Mario bros when Mario is the name of just one of them? 
@sidd_harth0_5h4h I'm not the best person to answer all of the questions, but i can answer this one. It's because Mario's full name is Mario Mario — https://nintendoeverything.com/miyamoto-says-marios-full-name-is-mario-mario/
Miyamoto says Mario's full name is "Mario Mario"

Nintendo’s famous plumber simply goes by the name Mario. But did you know that he has a last name as well? During Japan’s 30th anniversary Super Mario Bros. event this past weekend, Shigeru Miyamoto apparently stated that Mario’s full name is “Mario Mario”. As for Luigi, he’s “Luigi Mario”. It’s sort of like someone named Yamada Yamada having a brother...

Nintendo Everything
@uncoolmouse thank you