Research shows that hair type and texture are inherited. There is also an “additive” trait contributing to hair type and texture. This means the amount of curl in the hair depends on how many curly hair gene variations are inherited. Hence, two curly-haired parents may not always have curly-haired children because many different genes are involved. Curly-haired parents can also carry straight hair genes, which they may pass on. Genes can also interact with each other to determine hair texture. This is the reason why in a family, different people may have different types of hair.