​KembaraXtra – Legal Terms – Prohibited Degrees of Relationship


Prohibited degrees of relationship are family relationships within which marriage is forbidden by law. A marriage celebrated within a prohibited degree is generally void. Examples include relationships between grandparents and grandchildren, parents and children, siblings, uncles and nieces, or aunts and nephews. Although marriage is prohibited, not all sexual relationships within prohibited degrees necessarily amount to the criminal offence of incest. The rules are intended to protect family structure, prevent exploitation, and preserve social and moral standards. Historically, the law also prohibited many relationships by affinity, such as marriage with certain in-laws.


Modern reforms have reduced some of the restrictions relating to affinity relationships. Since 1986, certain marriages between former in-laws may be permitted if specified conditions are met. For example, a man may marry his former mother-in-law provided particular family members are deceased. The rules governing prohibited relationships are mainly contained in family and marriage legislation. Courts will treat a marriage within prohibited degrees as void from the outset, meaning it is regarded as never having legally existed. These rules therefore remain an important aspect of family law and the legal regulation of marriage.