Riddle #247

Question: Timmy's mother has three children. The first was named April. The next was named May.

What is the final one's name?

Question: What do you call a sad bird?

Question: What kinds of balls do dragons play soccer with?

Question: What can be broken but never forgotten?

Question: Where do all the letters sleep?

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?