Natasha:
Clint. He liked to make you laugh whenever your mother went on missions and you cried non stop. He was your appointed babysitter and if he ended up going with your mother, it was Steve. Natasha didn't trust you with Tony after he took you flying over the city and you slipped out of your blanket. She almost killed him.
Wanda:
Pietro. He enjoyed having you around and would often take you out for a walk in the park, eating ice cream and pointing out how slow other people were. You listened because you had no other choice, but you enjoyed the cold treat.
Bucky:
Steve and, surprisingly, Tony. Bucky trusted you with Steve and you loved Steve just as much as your dad did. You also liked being around Tony because he would sneak you into his workplace to show you all his cars. The one time he took you out for a drive was the last time when Bucky found out you weren't in a car seat. You rarely saw him after that.
Tony:
Bruce. If Tony and Pepper needed a break, he was the one to take you in and entertain you until your parents woke up from their seven hour hibernation. Often, you'd fall asleep on his shoulder while watching Sesame Street.
Clint:
Natasha. She had no problem babysitting you. She was practically a baby whisperer and would put you to sleep in a matter of minutes. You were never fussy with her and loved to play with her red hair.
Steve:
Bucky. He loved to babysit you, although he had his own fears that Steve quickly put to rest. You loved snuggling up against his metal arm when it got hot and he wouldn't move an inch until you woke up.
Thor:
You loved them all. You didn't get to see them a lot, but when you did, you enjoyed spending as much time as you could with all of them. Although you had to admit, your Uncle Loki had a special place in your heart.
Bruce:
Tony, no doubt about it. He was the fun uncle that often drove your dad crazy, but would make up for it by babysitting you when he got busy in the lab. He spoiled you rotten and you loved every minute you got to spend with him because he would take you anywhere he could.
Pietro:
Wanda. You loved playing blocks with her because she would build you the biggest castle with her special powers. She also sneaked you lollipops when Pietro wasn't around even though he told her not to encourage your sugar eating habits.
Loki:
Thor. He would give you piggyback rides that left you breathless and Loki didn't like when he threw you up in the air, but you'd plead for him to do it again. Loki would concede with a hidden smile on his face.