a question about High School DxD trading cards.

so i was wondering why most of the card sets from more than a year ago weren't parented? and if i could fix that.

some examples
post #3165758 -> post #3165759
post #4014711 -> post #4014712
post #3842836 -> post #3842837

Those appear to be part of the same set, kinda like kantai collection/azur lane/girls' frontline ruined clothing variants (kantai_collection torn_clothes official_art parent:any), so yes I'd say they should be parented properly.