Do Both Twins Have Bunions?  Exploring Bunions & Twins

The rate of identical twins (developing from the same egg) around the world is the same – about 3 in 1,000 births, while the occurrence of fraternal twins (two different eggs are fertilized by two different sperm cells) is nearly twice as likely – about 6 (in Japan) to 20 ( in some parts of Africa) in 1,000 deliveries, and varies geographically.  Fraternal twins occur at a much higher rate due to hereditary predispositions and the use of fertility drugs, etc.

According to researchers who studied 130 pairs of twins; 74 sets of identical (monozygotic or MZ) twins and 56 pairs of fraternal (dizygotic or DZ) at the Royal Melbourne Hospital, the Twin Research Study concluded that while genetics play a role, lifestyle choices had a higher degree of association.

However, that being said if your twin has bunions, you are 4 times as likely to have a bunion as shared habits such as footwear choices (wearing similar style shoes) were a stronger factor than genetics alone.

Those twins who were identical did have a higher correlation (.50) versus fraternal twins (.33), however statistically speaking, there was no significant difference in those numbers since age and same-sex again results in higher likelihood of similar environmental and lifestyle choices.