Two teenage brothers have been convicted of sexually assaulting their six-year-old sister at their family home in Birmingham.

But a jury at Birmingham Crown Court was discharged after failing to reach verdicts on rape charges following a two-week trial.

The defendants, aged 15 and 13, had denied abusing their sister at the family home between September 2006 and May last year.

The 15-year-old boy was convicted of four counts of sexual assault of a child. Two of those counts related to indecent behaviour with another sister.

The second defendant was found guilty of two counts of sexual assault, both relating to abuse of the six-year-old girl.

Prosecutors told the court they did not wish to offer any further evidence relating to the rape charges. Both boys were ordered to sign the sex offenders' register.

Her Honour Judge Thomas, who will sentence at a later date, said: "In spite of their ages the law requires that they must sign the Sex Offenders Register.

"These are very worrying offences for such young people to have committed."

The case was brought to court after the children's mother contacted the authorities last summer.