Mario & Luigi: Paper Jam

[Koopaul]

This is most confusing when you think about it. This means that the Paper Mario series is an alternate universe, which means certain characters (like Goombella and Vivian) don't exist in the same world as other characters (Fawful and Popple).

But does this mean that neither M&L series and Paper Mario series take place in the same universe as the main Mario games?

Is every spinoff an alternate universe?

I-I'm so confused...