At 3rd level, paladins gain the Sacred Oath feature, and the Oath of Betrothal is a new option for paladins.

Oath of Betrothal

"LADY TAIGA, YOU REALLY MUST BE MORE CAREFUL," Eryck the Diviner said with a deep frown. "Why do you always put yourself in such danger just for my sake? You don't go nearly so far for our other comrades."

Caught in the middle of cleaning her own blood off a set of battered battle armor, Lady Taiga spluttered momentarily before answering. "I-it's not like I LIKE you or anything!" she said. "It's just that—what if we find a magic sword, and you're too unconscious to identify it? How will I enjoy my Holy Avenger then?!"

As they argued, the rest of the party only rolled their eyes. The blush on Taiga's face made the truth far too obvious.