Good Riddles

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

What are they?

Question: What do you get when you cross a cheetah and a burger?

Question: What kills a lot of people but is harmless?

Question: What grows shorter as it grows older?

Question: There are 2 brother's, the oldest is 4 yrs old. The little brother Is 1/2 his age. When the big brother is 100 how old will the little brother be?