Suppose if mother and father belong to the same community and are cousins. Unfortunately, the mother has a defective gene that can be a cause of illness for the child. Since the father is also part of the same community, it is highly possible that he also has the same defect. In such a scenario, the child gets the defective gene.
For more detail, visit:
https://activatednaancestry.wordpress.com/2021/05/26/how-are-first-cousins-different-from-double-cousins/
How are first cousins different ..
You and your sibling share 50% DNA of your mother and father. However, the DNA distribution is not the same in both of you. The distribution of DNA is random. S..
https://activatednaancestry.wordpress.com/2021/05/26/how-are-first-cousins-different-from-double-cousins/