<p>Each parent has 2 sets of genes for skin color.</p>
<p>Obviously each parent had a set of ‘white’ genes for skin color (I think there are 8 genes coding for skin color so far found) and the paler baby got all those. For their second set of genes, the parents had some combo of white to ‘dark’ genes for skin color and the paler baby managed to inherit all those white genes.<br>
The other baby snagged about 3 or so ‘dark’ genes. The ‘dark’ genes which code for melanin trump the ‘white’ genes that the darker baby inherited, so he expressed darker skin.</p>
<p>It will be interesting to see whether the skin of the “white” twin darkens as he gets older, something that typically happens with black babies.</p>
<p>Northstarmom, it actually did happen in a case but both babies changed opposite colors. </p>
<p>“In 2006, Kerry Richardson, who is of Nigerian and English descent, and her partner, who is white, gave birth to twins who were both born light-skinned. But as they got older, one got darker while the other got lighter.”</p>
<p>I don’t know if you guys watch big brother, but in the new season the black woman, Libra, she has twins one white one black. They were adorable.</p>