Er, okay. But you'll not get a more similar environment that a home shared by siblings. And if despite such shared environment siblings don't turn out identical, then that 50% genetic difference is where it's at.
For some reason you seem incapable of grasping the simple concept that genetics most likely determines potential capacity but environment and life greatly influence actual capacity.
There are shared environments and non-shared environments; but genetics predominates. Maybe that's where everyone can agree? Here's an example. Three and four year-old children who attended Head Start enjoyed some benefits from the program. But these benefits are mostly gone by the third grade. Why would that be? Because traits, or your genetic potential, become more heritable as you age.
Head Start Advantages Mostly Gone by 3rd Grade, Study Finds