Brother

He is not a toy, no.
Just like a shining star,
he goes wherever I go.
Although he’s very small
and not so very tall,
secretly tucked away
hidden in my treasures.
It reminds me when I am not with him;
We would laugh and talk all day,
we would share lots of secrets,
secrets of all size.
Who is this person, you say.
Can you guess who he is?