Image copyright Getty Images Image caption Mary Kay Fualaau (left) served a prison term for having sex with Vili Fualaau before marrying him in 2005

A husband has filed for legal separation from his wife and former teacher, who had served a jail term for having sex with him when he was 12.

Vili Fualaau, now 33, submitted papers to a court in Washington state, US, to end his 12-year marriage to Mary Kay Fualaau (formerly Letourneau), aged 55.

Mrs Fualaau was a married 34-year-old mother of four when she began a relationship with him.

After she had served her prison term, the pair married in secret in 2005.

Mr Fualaau filed for separation early this month without stating the reason for his decision, it has emerged.

In the petition, he writes that neither he nor his wife own any property or have debts, US media report.

Mr Fualaau, who has two children with his wife, also states that they are no longer dependent, asking for a fair division of the couple's joint assets.

His wife has so far made no public comments on the issue.

Mr Fualaau was a sixth-grade student when the relationship began in Seattle in 1996.

The teacher was arrested in 1997 when she was pregnant with the couple's first child, and later admitted second-degree child rape.

Her initial six-month sentence was then commuted to three months - under the condition that she would have no contacts with her former pupil.

But within weeks the pair were caught having sex, and she was jailed for seven years.

She gave birth to the couple's second child in prison.