Yes, it is possible for two brown-eyed parents to have a blue-eyed baby, though it is relatively rare. The eye color of an individual is determined by the combination of genetic factors inherited from their parents.
Eye color is primarily influenced by the amount and distribution of a pigment called melanin in the iris, the colored part of the eye. The specific genes responsible for eye color inheritance are complex, and multiple genes are involved in determining the final eye color outcome.
Brown eye color is dominant, meaning that if a person has even one copy of the brown eye color gene, they will typically have brown eyes. Blue eye color is recessive, meaning that it requires two copies of the blue eye color gene to manifest as blue eyes.
If both parents have brown eyes, it suggests that they likely carry at least one copy of the brown eye color gene each. However, they can also carry a recessive blue eye color gene, which may not be expressed in their own eye color but can be passed on to their children.
If both parents are carriers of the recessive blue eye color gene, there is a small chance (depending on the specific genetic combination) that their child could inherit two copies of the blue eye color gene and thus have blue eyes.
While it is less common for two brown-eyed parents to have a blue-eyed child, it is still possible due to the complex nature of eye color inheritance and the presence of recessive genes.