Production for Captain America: Civil War is in full swing and, as such, information about casting is about to become much easier to come by. The other day came word that Martin Freeman had joined the cast (God, I hope he gets to interact with Doctor Strange at some point, if he sticks around in the MCU!), and now comes the news that Emily VanCamp will be appearing in the film. VanCamp will be reprising her role as Agent 13, aka "Kate," aka (to comic book fans) Sharon Carter the niece of Agent Peggy Carter.
In Captain America: The Winter Soldier, her character was introduced as Cap's neighbor Kate, who we discover to secretly be working for S.H.I.E.L.D. as covert security detail for Steve Rogers. What hasn't been established yet in the films is that she's the niece of Steve's old flame Peggy, the titular character of the ABC series Agent Carter.
There's no word yet on whether that relationship will be explored in Civil War, but now we know that the possibility exists.
VanCamp just wrapped a four season run on ABC's Revenge.