In the sewers, you were walking around when you sat down and tried not to cry when
??: hey dudes!! We can't leave her here!!
??: Mikey's right! We can't leave her!
??: Master Splinter will understand! Let's bring her!
??: YEAH BOY!!!!!!!
??: MIKEY!!!!!!!!!
??: *softly* yeah boy!!!
At the lair, Master Splinter agreed for you to become their little sister
Donnie: guys! Y/N has 25% of each of our DNA!
Mikey: and?
Donnie: She IS our baby sister!!
All: she is!?
Donnie: yeah!
They smiled and they saw you sleeping on the couch so they picked you up and took you to bed
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TMNT Little Sister
Fanfiction(Pretend its not April) The turtles find you when you were 4 years old and they took you in as their baby sister. But what happens if they find out you are 25% of their DNA. What happens if Shredder is looking for you and your bros?