What Am I Riddles

Question: I am a nice word composed of five letters, but the Romans would call me a numbers.

What am I?

Question: It takes one word to separate them; otherwise they are inseparable.

What are they?

Question: Whoever makes me can hear me, but nobody else can.

What am I?

Question: I am shorter when I stand and taller when I sit.
Sometimes I'm even called a pit.

What am I?

Question: A father goes to prison and the mother will have to sell her hotel, but their young daughter is happy.

How can these parents tolerate such ingratitude and what put them in this situation?