Logic Riddles

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

What am I?

Question: When I was 2 years old, my brother was half my age. Now I am 100 years old, how old is my brother?

Question: There are three men in a room with 62 Bicycles. two men are mad at the other man. Why?

Question: There was once three trees. The first tree did whatever the third tree did, and the third tree did what ever the second one does. What happens if tree number two gets cut down?

Question: What is yours, but only others can use it?