Toy Broom Question About Harry Potter And The Deathly Hollows, About The Letter From Harry's Mom? *SPOILER ALERT*?

Question about Harry Potter and the Deathly Hollows, about the letter from Harry's mom? *SPOILER ALERT*? - toy broom

Did not I read that last part, but please do not spoil anything for me.

Have in the letter from Harry's found, Serius sent his mother says she loves toy broom Harry. Harry talks about a one year increase on her broom, but in the first book and the movie is Harry a child when his parents are murdered, and he was sent to his aunt and uncle. So, how is it possible, Harry was not even a year, but if their parents have died.