/sci/ - Science & Math

Scientifically speaking, should it be possible for a 10 year old boy weighing 60lbs and 4'7 tall to be twice as strong as an 18 year old man weighing 123lbs and 6'1 tall?

Well I had to supervise my 10 year old brother at the gym, I don't usually go but my dad couldn't go to with him so I had to go. He could bench 85lbs and I couldn't bench the bar (45lbs).

Then when we got home, we arm wrestled with my 2 arms versus his 1 and he won. How is this possible? Do 10 year olds have enough testosterone to be that much stronger than an 18 year old? He's not even a particularly strong looking kid, that's him in the pic attached. He looks like a nerd.

Could it be a misunderstanding? Do arm wrestles and bench presses constitute strength? Please don't roast me, stick to scientific answers. And this is not a /fit question, I don't want advice on how to improve.