Is Waluigi Wario’s Brother
Absolutely, as are all continents.
Waluigi and Wario are boyfriends who liked to cosplay as local celebrities Mario and Luigi, but then Nintendo sued them so they had to make their costumes legally distinct.
Yes
No, he’s just his friend
Is Toad bald under the hat?
Asking the real questions.
Waluigi and Wario don’t know each other
Waluigi is just some guy
No, continents are not islands. Yes this is as arbitrary as whether pluto is a planet.