I want something that's similar (Not 100% like it) to this: A girl and a guy are like the same, they have the same strength and same fashions sense, and they have been raised together from childhood. The girl starts to change and become more girly and more weak compared to the guy.
I don't care about the plot, I just kind of want this to be in the story.

Your mom goes to college.

1. Superior
2. Gintama
3. The bride of the water god
4. Chevalier D'eon

Hmmm... maybe Strange Orange? I don't know about your tastes so you may think it looks too stereotypical-shoujo, but I've found the characters and story to be a lot of fun!

And a couple that don't entirely fit...
The protagonists of Kare Kano meet in high school, but are more or less equal in terms of intelligence/etc. I don't know that Yukino becomes weak, but maybe... she lets herself depend more on others than just herself?
3 Years has a boy and girl who, again, meet when they start high school, but their appearances (and behaviour?) are similar at the beginning.

In most of the titles I've read about "childhood friends," the girl is the tough/aggressive one while the boy is weak... and then of course they grow up to be the opposite. That doesn't sound quite like what you're looking for, but it's a staple of shoujo manga (I'm getting a little tired of it myself).

Well in Lovely Complex the guy and girl have really similar tastes... and they knew each other quite awhile b4 they started having feelings...
And I strongly recommend Gokinjo Monogatari. The guy and girl grew up together ... but they dun really have the same tastes (they both go to art school tho)... Also, the guy has always been 'protecting' the girl since they were young. Still, it's an awesome read.

The first manga that flows into my mind is Kirameki Gingachou shoutengai

The guy and the girl knew other since born. They live next to each other, have the same height and weight at first, but the boy becomes stronger and taller later. Though their fashion senses are completely different.

Quote from qiqi92sg

And I strongly recommend Gokinjo Monogatari. The guy and girl grew up together ... but they dun really have the same tastes (they both go to art school tho)... Also, the guy has always been 'protecting' the girl since they were young. Still, it's an awesome read.

I second Gokinjo Monogatari 😃

Quote from Mamsmilk

Quote from x0mbiec0rp

Quote from Mamsmilk

I need a die with 2 sides.

That's known as a "coin".

Oh, thanks. Too much D&D.