The simple answer is genetics and not hair products or remedies. However, when it comes to genetics, it can get pretty complicated.
To give you an example of how genetics work – suppose that girl has a straight dark hair that is similar to her mothers. In this case, it is true that her hair has identical features to her mother’s hair, but she also has the genetic information about the texture and hair color from her dad.
While this may seem straightforward, you can add in the complication of dominant and recessive genes. Overall, it can be said that understanding most of the hair traits is a very complicated task. Your hair is the result of the interaction of your parents and does not depend on a single gene.
Hope this helps!