It is a punishable offence but as it usually happens between closed doors and is interpersonal it is hard to enforce the law against incest particularly if it is done with mutual consent. It also refers to child sexual abuse in certain contexts. Incest can happen in any family and can happen one time or be an on-going problem. It is a violation of trust and authority that the child places on that person.
The primary reason for laws against incest are to avoid multiplication of genetic defects in the population, nothing to do with morals. Incest is far more common than people generally will admit.
2 deranged psyco's who are related, who can't get dates outside their own family.
Incest is a sexual relationship between immediate family members. It may, or may not, apply to cousins. That would depend on the family.,
There is NO truth in the report that one man set fire to his sister because he didn't know the difference between incest and arson.