But it will not be punished if the person in question has been under 18 years old when have performed the sexual act with parent or grandparent or the person have been forced or illegally persuaded to perform the sexual act. Thailand[ edit ] Incestuous relations between adults over 18 years old are not prohibited by law. It is punishable by up to 9 years in prison. The degree of relationship is calculated vertically, therefore a sibling is within the second degree of relationship. The marriage, being valid under the laws of the place of celebration, was then recognized for immigration purposes only. Singapore[ edit ] Section G of the Penal Code specifies that "a male, of or above the age of 16, having sexual relations with his grand-daughter, daughter, sister, half-sister, mother or grandmother, with or without consent, shall be guilty of an offence. The act does not refer to other familial relationships such as grandson-grandmother , or same-sex relations. Any woman of or above the age of 16 years who, with consent, permits her grandfather, father, brother, half-brother, son or grandson whether such relationship is or is not traced through lawful wedlock to penetrate her in the manner described in subsection 1 a or b , knowing him to be her grandfather, father, brother, half-brother, son or grandson, as the case may be, shall be guilty of an offence. Incest between relatives who are minors below 18 years old at the time of offence is not punishable but remains a crime, therefore aiding and abetting of incest between related minors is punishable. Bautista, an Immigration Officer denied entry to a married couple who were second cousins. However, during a speech made during the second stage reading of the bill in March , Justice Minister Alan Shatter TD stated that while he was not opposed to the bill in principle, a sexual offences bill announced by the government on 17 December will "include measures to equalise upwards the penalties for incest by male and female offenders" and also "take a more comprehensive approach to reform of the law in this area". However, on appeal, it was found that the parties were collateral relatives and therefore fell under subsection 2 of the same Code, which prohibits marriages between relatives by blood within the fourth civil degree. Sex between siblings is punishable by up to 2 years' imprisonment. Republic of Ireland[ edit ] Incest is illegal in the Republic of Ireland under the Punishment of Incest Act ,  which pre-dates the foundation of the state. Article of the Penal Code prohibits sexual intercourse between any lineal relatives by blood or collateral relatives within the third degree of relationship by blood. Turkey[ edit ] Sibling marriage and avunculate marriage is prohibited, while cousin marriage is legal. The Judicial Yuan Interpretation No.