Good Riddles

Question: Although I'm far from the point, I'm not a mistake.
I fix yours.

What am I?

Question: People see through me, but none pass through without killing me. I can be anywhere, and can be seen double or single. What am I?

Question: Two children are born in the same hospital, on the same year, on the same day, and have the same father and mother. But they are not twins.

How is this possible?

Question: I attach to your hip and I sing all day.
All I want to do is play.

Question: If you have two twins, three triplets and four quadruplets; how many people do you have?