Sharon Carter

Sharon Carter is a relative of Peggy Carter and an agent in S.H.I.E.L.D., who appeared in Captain America: The Winter Soldier. She is portrayed by Emily VanCamp.

Captain America: The Winter Soldier
Towards the beginning of the film, Sharon is undercover as "Kate", a neighbor of Captain America. Sharon is a young, attractive S.H.I.E.L.D. agent with skills in martial arts and weapons whose mission is to guard Steve Rogers — and not let him know it. She is guided by a strong moral compass and is not afraid to speak out when her ethics are challenged.

Trivia

 * In the comics Sharon Carter is the niece of Peggy Carter. The original comic's time jump from the 1940s was only twenty years, making it plausible that Sharon was Peggy's niece. Considering the time jump for the films is from the 1940s to present day, it is more likely that Sharon will be portrayed as Peggy's granddaughter, although this is unconfirmed.
 * In the comics, Sharon eventually fell in love with Steve Rogers becoming the primary love interest.