the person in the relationship who is of greater benefit. they are so in love and believe that they are of the most fortunate amongst the world. He is loving, caring, protective and always fails to do something wrong.
Kirstin is the lucky one in the relationship. Her boyfriend is the best thing any girl has ever laid eyes on.
'lucky one' or "the lucky one" is a term describing the person most fortunate in a particular circumstance or relationship
For Example: Mara is the lucky one, because Jessie is super funny, has cool hair and always treats her like she's the best girl in the world, even though she's a big nerd. It must be great to have such an awesome boyfriend.