I am going to be so disappointed if this all boils down to MM and Regina having feelings for the same boy. If all of this is because REGINA wanted some boy that only had eyes for SNOW.
I think the reason REGINA ends up married to King Leopold is it was an arrange marriage. After Snow’s mother dies the match is arranged to cement relationships between the kingdoms OR to get $$$$$ for the realms coffers.
REGINA has feeling for some commoner / the stable boy, but he only has eyes for SNOW. Maybe the boy gets banished / killed and that is why REGINA HATES SNOW…
1/ Snow stole the boys affection
2/ Snow some how reveals the relationship between Regina and the boy to Regina’s mother. … thus getting him killed or banished.
3/ Push it further and AUGUST / STRANGER is the boy they both had the hots for.