Both pairings involve a woman who is born into royalty and a man who is a criminal or outlaw.
Both couples involve a hero and a redeemed villain.
Both couples are second 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.
Both pairings were confirmed as True Love by means other than a True Love Kiss. Regina was led to Robin using pixie dust, while Emma and Killian passed the Underworld's test to access the ambrosia and also reunited using a pixie flower.