There is a rare group of fraternal (non-identical) twins born to parents of different ethnic backgrounds.

The most recent set involve two little girls born to Caucasian mother, Whitney Meyer, and an African-American father, Thomas Dean. The girls, now nine months of age, are named Kalani and Jarani.  Kalani has light skin and blue eyes, whereas Jarani has darker skin and brown eyes. The twins’ physical differences can be explained by the fact that two siblings share 50 per cent of their genes, on average. You can read more about the story that is exploding the internet here.

Complex traits, like skin tone, are under the influence of many genes, perhaps twenty, and interactions among them, as well as environmental effects are responsible for appearance. The two twins simply inherited different sets of genes from their mother and from their father, making these ordinary twins look extraordinary.

In my forthcoming book, Twin Mythconceptions, I write about several other such fascinating cases and include info about embryology of twins, twin types, intellectual growth, personality traits, sexual orientation of twins, marital relationships, epigenetic analyses, and more. Five appendices cover selected topics in greater depth, such as the frequency of different twin types and the varieties of polar body twin pairs.

Twin Mythconceptions will publish in mid-February. If you would like to pre-order a copy of the book, visit the Elsevier website. Apply discount code STC317 and receive 30% off the list price and free global shipping.