Mario loves all his niblings equally, but he definitely spoils Magma the most, because she's the babiest (and she still calls Mario her mama and that's what led to him getting baby fever to begin with 🧍)

Magma's very young and when she's told she's going to have a cousin, and then she's told they're twins, she doesn't understand that at all, but zio mama and zia Peach look very excited, so she's excited too!

Thing is, she still doesn't quite get it- so she still asks for uppies from Mario (and that's on him, he spoiled her that way) and his back hurts a lot and all and yet he holds her (most likely to do it sitting down at the last months tho), and sometimes she looks at his growing belly weird, like she's not sure why it's so big suddenly, and Mario or Luigi each time explain it's her baby cousins in there.

Luigi is told by Mario right away that he's pregnant, over the phone, so he's all excited and talking hurriedly in Italian and Bowser besides him is like >:3 ? (bc a few minutes ago they were snogging, until Luigi's phone ringed for the second time, and he picked up only bc it said it was 'fratellone'). When Luigi hangs he excitedly tells Bowser that they're going to be uncles, and maybe it takes a few seconds for his husband's words to process but when they do he's like What?! Red's gonna have a baby? Nice for them!

Anyways- imagine those big siblings that are still babies themselves and then get a new baby sibling... Mario is Magma's favorite uncle ever (maybe even her favorite person after mama and papa), so when he suddenly has a baby on his arms and showing it to her she's like ?? and not only that, but Zia Peach has an exact same baby on her arms too. And we'll, she's like jealous of the babies all of a few hours until Mario goes back to hold her and snuggle her face, and even let's her pat the babies blanket-wrapped bodies for a bit, and she likes them right away.