Why are parents and children related to the same genetic degree as siblings?

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consanguinity (Left) Absence of inbreeding: horizontal lines connect mates, vertical lines connect parents with their child; (right) an inbreeding loop: horizontal bar at top of loop connects brother and sister, all other lines and bars as above

Parents and children are related to the same genetic degree as siblings because both relationships involve sharing approximately half of their genetic material, leading them to be classified as consanguineous in the first degree.1

A child inherits about one-half of their genetic information from each parent, establishing a direct 50 percent genetic overlap. Similarly, siblings share about half of their chromosomal constitution because they inherit their genetic material from the same set of parents. While the exact fraction can vary due to the random nature of meiosis—the cell division process that creates sperm and egg cells—the statistical likelihood of shared genetic potential remains the same for both relationships.21