How are Wario and Waluigi related?

[CM30]

Are they brothers? Cousins? Are they related at all?

Cause a few games, as well as other media like Wario's Warehouse, called them brothers (Mario Party 5's 'Wicked Bros' label being the most prominent), whereas at least one Mario & Luigi game called them cousins and Charles Martinet apparently once said they were unrelated.

Nintendo themselves and the mainstream Mario games seem to constantly change their mind on the issue, or don't bring it up.

So how are these two related?

 

[Hastagazpatcho]

aa

 

[SurrealBrain]

I like to think they're brothers, if for no other reason than just because.

But yeah, I do wish Nintendo would make up their minds on the issue. But then it's create a whole new debate on whether or not it should be that way, with one group saying "I knew it!" while another says "No, it shouldn't be that way," so maybe it's for the best.

 

[WarioTime!]

It is confusing, but for me they are brothers. Since Waluigi was created as a parallel to Luigi it makes sense.