name of a book?

[jenn twilight <3]

i read this one book in 5th grade and it was really good! i wish i could remember what it was called though! i borrowed it from a library so it isn't mine and i can't ask the library for a list of books i've checked out cuz i lost my card and got a new one so my old account got erased.

so maybe you know what i'm talking about if i described the story?

so there's this guy and he basically lives in his attic cuz this was a time in america when parents could only have a certain amount of kids (i think it was 2 or 3) and people weren't supposed to know he existed. and then somewhere in the neighborhood, he suspects that there's another kid like him, that isn't supposed to be known. and one day (i don't remember how) he actually meets her. i think he snuck into her house or something. and her name's jen. i seriously wish i remembered the name of this book.... like these kids couldn't go to school, couldn't be seen in public, nothing

thanks for your answers in advance!! =)