You're the actual child of Robert baratheon but since you didn't look like you're siblings, you were called the bastard child of cersei...because everyone still believed Joffrey and his other siblings are Roberts...you were given the last name Snow instead of sand because you were born on a trip to winterfell...but was still raised in the castle...and Robert still took care of you as his own

You and Joffrey were close growing up...you are his favorite sibling and your the only one who could get him to listen or to be kind...but you're mother cersei hated you with every ounce of her heart so when you were six...she sent you away without anyone's knowledge...everyone thought you were kidnapped...you were bought as a slave...but you weren't one of the pleasure one's thankfully...you were one of the fighters that would be sent into a fighting pit [even if you're a girl...because they had no other use for you]...but you got good at fighting...and won every fight you were given...but you were so young and now very traumatized...you prayed for the mother's mercy and forgiveness every day...and the warriors strength.

Years passed...You heard Joffrey is king, you wish you could have been there for him...but you ended up getting lucky...you were able to escape...you snuck aboard a ship...and made it back to kings landing...you look similar to your father, Robert and a bit like your mother, Cersei...but more towards Robert, the younger Robert ofc.