Except, that is, they are brother and sister.
This BBC article discusses a rare instance where a set of twins were separated at birth and adopted by different families. They grew up without knowing each other, met later on, fell in love and got married – only to then to find out that they are related. This is one of many reasons why I, and other mental health/public health/sexual health professionals feel that it is important to be honest with individuals about their birth and their identity.
(Thanks, M.)
