As a teen, i was always wondering about the size of my penis... Average or not? Like Dad or not?
I saw Dad in briefs but it was hard to tell what size. One day, he was undressing and i had the chance to see him naked. I think that he sensed my curiosity. No big deal about it... He has a penis, me too... He had already seen my teen's penis when i sought for advice about some bleeding on the part connecting the foreskin to the head.
From this experience, i knew that i was average... same as Dad!
So it's normal for a guy to see dad's penis.