no, it does not matter if they are just fictional characters. Frisk is darn child, don't ship them with adults, please.
"BUT THATS NOT CONFIRMED!!!!11!!1"
-Never does the game imply that Frisk is an adult, or that Sans and Papyrus are children. Instead, it practically tells you the exact opposite throughout its entirety.
"PAPYRUS ACTS CHILDISH THO?? AND THEY EVEN DATE IN CANON !"
-A childish adult doesn't stop being a physical adult. And frankly, if you know how the "date" starts and ends, you will realize that it never confirmed any romance, but rather a friendship between them.
"BUT IM AGING FRISK UP!!!111!"
-Honestly if you need to change a key element of a character for the sake of a ship, then why ship them in the first place? Would you be comfortable if someone did this to you?
"IT'S AN AU, SO IT'S A DIFFERENT REALITY WITH DIFFERENT CHARACTERS!!!!"
-If it really were different characters in a different reality, then it wouldn't be Frisk or Sans/Papyrus. But that's not the case.
"WHO CARES IF THEYRE A CHILD, SHIPPERS GONNA SHIP LOLOL"
if you wish to curate just ask in the comments. i'll try to keep a low number of managers, though, so don't ask THAT.
Anti Matsu x Matsu: https://scratch.mit.edu/studios/2952018/
Anti ships like that i general: https://scratch.mit.edu/studios/3429079/activity