Both pairings involve a woman who is born into royalty and a man who is a common-born criminal of outlaw.
Both couples involve a hero and a redeemed villain. Both villains were seeking revenge for the death of a vorige love.
Both couples are seconde chances at love for all characters involved. Emma's first love was Neal Cassidy while Killian previously loved Milah. Regina previously loved Daniel while Robin was married to Marian.
Before Regina let Daniel go in The Doctor, he asked her to love again. Before Neal died, he asked Emma to find Tallahassee - their hoped location for a happy future...