Cousin Corbin's dogs

While driving to preschool, Avery and I were discussing his Aunt and Uncle who are about to have a baby.  I was explaining that he and Aileen may get to have a new baby cousin, and I was helping him understand which aunt and uncle they were - "the one with the dogs".  Avery wanted to go and visit them, and I said that we might be able to.  Then, with a concerned look, he asked if their dogs "eat people?!".  I reassured him that they don't.  He then asked why they didn't "just have a cat?".  Before I answered, he reasoned with himself out loud "Oh,....they probably don't have a cat because they are poisonous, right?"