Winter Widow

Natucky is the romantic relationship between Natasha and Bucky, sometimes called Winter Widow, Soviet Spouses, Soviet Soulmates, or Red Room Romance.

People like the ship because of their involvement in the red room, as well as the way their personalities interact. Natasha is portrayed as stoic and Bucky is portrayed as the guy you don't cross, according to the fans, but this ship is not canon.