Am I too old?

兒子生日收到不少生日賀卡。 他雖看不大懂， 卻認出了"old" 一字。
Son："Mom, Am I too old?"
Mom: " Not that old."
Son: "Then what did they say?" point out the birthday cards.
Mom:" They said "Happy Birthday , You are 5 years old!" "
Son: "But they still said OLD".
Mom : " yeah, they are so mean".