(1)A person aged 16 or over (A) commits an offence if—
(a)he intentionally penetrates another person’s vagina or anus with a part of his body or anything else, or penetrates another person’s mouth with his penis,
(b)the penetration is sexual,
(c)the other person (B) is aged 18 or over,
(d)A is related to B in a way mentioned in subsection (2), and
(e)A knows or could reasonably be expected to know that he is related to B in that way.
(2)The ways that A may be related to B are as parent, grandparent, child, grandchild, brother, sister, half-brother, half-sister, uncle, aunt, nephew or niece.
(3)In subsection (2)—
(a)“uncle” means the brother of a person’s parent, and “aunt” has a corresponding meaning;
(b)“nephew” means the child of a person’s brother or sister, and “niece” has a corresponding meaning.
(4)Where in proceedings for an offence under this section it is proved that the defendant was related to the other person in any of those ways, it is to be taken that the defendant knew or could reasonably have been expected to know that he was related in that way unless sufficient evidence is adduced to raise an issue as to whether he knew or could reasonably have been expected to know that he was.
(5)A person guilty of an offence under this section is liable—
(a)on summary conviction, to imprisonment for a term not exceeding 6 months or a fine not exceeding the statutory maximum or both;
(b)on conviction on indictment, to imprisonment for a term not exceeding 2 years.