Good Riddles

Question: There are two sisters: one gives birth to the other and she, in turn, gives birth to the first. Who are the two sisters?

Question: A town only has one barber (he is male). The barber only shaves all of the people who do not shave themselves.

So who shaves the barber?

Question: A man and his boss have the same parents, but are not siblings. How is this possible?

Question: What has four legs and can't walk?

Question: Something all men have,
but all men deny.
Man created it,
but no man can hold it.

What is it?