Avengers, little Parker,

Not much is said about Peter Parker, his , being cared for by his aunt, bullied at school, not very popular, taken under Tony Stark's wing, spider man,

But to everyone's surprise he has a little sister Peyton Parker, six years old, she knows about Peter being spider man, she knows everything about every avenger thanks to Peter telling her stories,

But why did none of the avengers including Tony know anything about her,