Tony : 

10 months ago was his last one night stand. One month after the one night stand he started dating Pepper. He had been dating her for 9 months when someone demanded that she see Tony. Her name was Emily. She handed Tony a little bundle and said "she's yours. I don't want her." She then left. Tony opened the bundle to see a little baby with y/h/c (your hit color) hair and beautiful eyes. Pepper came down and said "let me guess she's from your one night stand 10 months ago"

He said "yes" she said "we'll have you decided on a name?" He said "y/n, that's her name"

Bucky : 

Bucky was walking down the street when he heard a scream. He went to the source of the scream and found a women with a gun shot wound in her heart. She said "please take my baby. Her name is y/n. She has special powers. She is one month old." He said "I promise to protect her" He called 911 to come get the lady and tell her family. He said "well y/n let's go back to my house"

Peter : authors note : in this he is Tony's biological son and Morgan is born also Tony is alive

Peter was in patrol when he asked a lady for a pen she handed him a baby in a blanket and said "I don't want her she's a freak with powers" Peter said "I think I'll name you y/n, let's go home"

Scott and Hope : 

12 hours of labor. That what Hope went through. Scott was by her side the whole time. While they were weighing and measuring the baby Scott got in the bed with Hope. Scott said "You were amazing" she said "thank but we need to think of a name for her" "what about y/n" said Scott. "I like it" when the nurse came back she asked what the name was and they told her the name was y/n. Hope held y/n in her arms while Scott had his arm around Hope and his hand holding y/n's. Scott was so thankful to have the 2 most beautiful girls in the world as his. 

Sam : Sam's ex-girlfriend had just showed up at his house. He invited her in. She handed him a baby and said "she belongs to you. I don't want her. She has powers and you are smart so here" She lady and he said " I think I'll call you y/n"

Loki : He found you in the woods on a rock and decided to keep you.