When I was in the 7th grade a close friend and I were fishing at a very secluded pond about a mile from our houses. We were drinking soda-pop and soon needed to pee. He was one year older, was going through puberty and his dick was pretty big looking and real hairy. I pulled mine out and I hadn't developed much hair and was still pretty small. He laughed and I didn't think any more about it. That is, other thank, screw him.
One day at school a girl came up and told me she'd heard my dick was only a couple inches long. I just told her it'd take more than her words to convince me of that. But... I knew who'd blabbed.
Move forward 3 years: I went fishing with the same friend. When I pulled my dick out to pee I was now a full sized man with a decent sized cock. His eyes bugged out. He wanted to know when that happened? I told him it wasn't too long after I'd entered 8th grade and it grew all year long and stopped at just around 7" erect with a large head and pretty thick.
He started in on me wanting to suck my dick and I let him. After his sucking for about 5 minutes I blew a young load into his warm, moist mouth. I told him I'd like to at least jack-off his shorter dick of about 5" but pretty thick. He pulled it out and I stroked him until I saw pre-cum starting to ooze out. I slowly lowered my head to his cock and began sucking it with great gusto. He didn't last but about a minute and blew a hot, creamy load into my mouth.
The following week a couple guys and girls came up to me and told me they heard I had a nice sized cock. I showed two of the guys after school and they were jealous of my thickness. One girl met me on the following Friday evening after a football game and we did everything but fuck. I didn't have a condom so we got each other off orally and she took my load in her mouth. Told me her jaws hurt a little.
I played with her and my good friend until we graduated. A couple years after that I met my old male friend at his folks cabin. No one else was home and we sucked & fucked all weekend. I topped him and stretched his ass but good.

Moral to this true story?

Don't let first impressions of a young boy or girl make you think they're inferior physically. Puberty causes many physical changes and growth of penises, pussies, asses and boobs. You'll love the difference.