Why I’m OK If My Son Never Says “I Love You”

My 9-year-old son has never said "I love you." I honestly never gave it a second thought until I realized I was being told "I love you" multiple times daily by my 5-year-old daughter. For the first time, I began to wonder why my son never said it, neither to me nor to anybody else that I know of. While I would never in a million years intimidate him into saying this phrase, the idea that he never said them made me a little sad.