A UK-based study shows that most commonly 10% of males and 15% of females have been involved or have experienced and/or experimented with some type of intimate contact with their siblings. The most common behaviour in such type includes the stroking of genitalia.  The intimate attraction between siblings or cousins who are related is very uncommon in most cases, due to a hypothesis known as Westermarck Impact, people who are living together through their initial developmental years may become desensitised to each other where sexual interaction is concerned.  Although, it is also known that family members who are separated at birth may feel intimate attraction, as they have always lived apart. It is also possible that brothers and sisters who live separate or rarely see each other, may develop such an attraction, and also in the case of step-siblings where the parent is not the same.