No they are not being grown, they are being found via math. All the bitcoins that can ever exist already do, a lot like gold. Which is why they metaphor the calculations as mining, you’re digging through the 1s and 0s to find another.
ALL money is completely made up, has no intrinsic value and is backed by nothing. That’s what money is.
Who sets the number of bitcoins? God set the amount of gold.
Bitcoin is made up, and whoever made it up can make up more.