you are thinking of identical twins. they are created by impregnated ovum splitting in two. that's why they look alike - they are literal genetic copy, defacto the same person. you can't distinguish them with a dna test.

fraternal twins come from two different eggs impregnated independently, growing up in the same womb. they are two different people, they don't look alike, they don't even have to have the same sex.

https://en.wikipedia.org/wiki/Twin