Which kind of twins are usually of the same gender? Are there other kind(s) of twins apart from #1? Are #2 also usually of the same gender?
Twin
Identical twins are always the same gender. However, identical twins are very rare. Most twin cases are formed from two different fertilizations during the same conception event. Non-identical twins can be opposite gender or same gender.
One of two offspring produced in the same pregnancy. Use with P31 on items for one twin
Are all twins the same gender?