What to say when a % year old asks

[redsox]

The other morning, my five year old son was between me and my husband as he and I slept. We awoke to our son holding my husband's penis. My son asked his Dad about his testicles and why Dad's penis was so much bigger than his. We simply told him that Dad is tall, that's why. Although I'm a sex therapist for teens and adults, we weren't prepared for our young son to have these questions.

So, how much should we explain to him at 5?

[javilu]

I imagine lots of Daddy's parts are bigger...his feet, his hands, his nose...