Welp...I went down an NSFW image search rabbit hole and, although far from being conclusive, my opinion is that yes, the penises are pretty much the same on identical siblings (saw a few triplets).

Classic nature versus nurture debate. Assuming identical male twins, anyway. Anything else and the answer is far more likely to be "no". Bob probably has a bigger D than his twin sister Sally. Probably.

But once you narrow it down, well, they really ought to be the same unless something significant happened to one and not the other. Note that the significance of that thing might not at first appear to be significant, however.

e.g. Maybe one time and only one time, Mom or Dad fed one of them twice by accident when the twins were infants and then had to the feed the hungry one "again" when he wouldn't stop crying (if they realised the error or not).

That one extra bottle of milk with no other differences might have made for a lifetime of difference between the two. And you still can't be sure which one would end up better endowed. Maybe something latent in the twins' genes would gives a hungry baby the advantage later in life, so to speak.

ETA: If this sort of thing is your cup of tea, you might find pictures out there on the internet. If it isn't, you might want to perform the same experiment using women's attributes instead. I understand certain forms of twin "art" are quite popular.

She's mad because she doesn't know the answer

I can actually answer this one. I'm a fraternal twin. I can confidently say that my dick is bigger than my twin brother's. As for how I know that... As kids we had no issues bathing together... And later in life we just never cared about either being nude. Nothing sexual just a straight up lack of feelings one way or the other.

Also I lived with him and his gf for a bit and she accidentally walked in on me as I was getting out of the shower and her exact words were "I hooked up with the wrong twin"... Unfortunately for her I'm gay.

Malfoy suppresses his rage. He knows for sure that Fred had a bigger dick, but has to settle with George's piece.

Aren't breasts mostly fat so they're more affected by nutrition?

Single vs multiple eggs twins, I assume?

Bau Bau ↘️↘️

I mean, most individuals have different size boobs.

brothers have one identical ball and one unique ball.

Thanks to the power of the internet....you can definitely answer this for yourself.

I have a science question. What factors contribute to growing a bigger dick?🤔

Up the interviewee’s butt. It brings him confidence.

it's very well hidden