I never fully read this comment and I've been re-reading our messages about SMG4 because I can't reply to your newest messages (can you maybe help me out a little on that?)
Anyways,
I don't know man, they have no real cannon feelings for each other, and I'm pretty certain that Mario lacks the ability to feel powerful emotions for less than 2 seconds (trust me, I know the feeling, I can't watch any part of a movie that is romantically awkward, for example when some dude gets nervous about proposing, or when a nervous kid tries say "I love you" to their crush. You know what, I think I'm just bad with emotions, but so is Mario.) He basically feels only a few emotions: Happy, scared, hungry(he's take hungry to an emotional level) angry(basically murder hobo), and loss/sad(ex. when Bendy sacrifices himself). Not once has he show capability of actual love, sure he seems to care when Luigi goes missing, but he always says something like "Now who's going to do all of Mario's laundry and cook Mario dinner..." He seems less to care about Luigi and more about what Luigi does for Mario, to the point where Mario probably wouldn't care about Luigi at all if Luigi didn't help him with everyday chores. He seems not to care about a person's personality or relationship with Mario.
Honestly this ties into one of the reasons I don't like the Axol x Melony thing (yes, I said it, I'm not a fan Axol x Melony) that reason is that when Axol first meets Melony
1. Axol is IMMEDIATELY interested
2. Axol didn't talk to Melony or anything
3. Melony was asleep, so Axol COULDN'T have known anything about Melony other than 'ooga booga manga brain see anime girl's
4. Even I you rationalize number 2&3 by saying 'oh well he might have known Melony's personality via talking with Melony before getting the mask' that doesn't put off num. 1, Axol was interested instantly, HOWEVER there is NOTHING to prove that Axol had a genuine interest in Melony BEFORE Melony got the mask
5. 1,2,3, and 4 lead to the conclusion, and one of the reasons I don't like Axol x Melony, Axol WENT OFF LOOKS. That is one of the most LOW BLOWS to go for. ALWAYS GO OFF PERSONALITY. I can't even begin to lists the reasons that personality beats looks. Now granted, Axol does seem to gradually care more about Melony from a personality perspective, but you can't erase the fact that he started it only on looks.