It is believed that the brother (who is now 14) began assaulting the young girl at the age of 4, and is said to have bribed his sister to keep everything a secret in return for Skittles.
Telling Brighton Youth Court, the mother revealed: 'She said to me 'Mummy I want to tell you something'. She didn’t normally say things with such an introductory manner.
‘It was something important to her. She said it happened while they were playing hide and seek.'
The mother further added: ‘She said she didn’t like it and didn’t want to do it. Afterwards I put her to bed and cuddled her and told her she was a very brave girl for telling Mummy.'
Speaking on the repercussions of the devastating account, her mother said: ‘I saw what I can only describe as a shadow come across my child’s face.
‘The shadow returns every time his name is mentioned. She was waking five times a night with night terrors.’
At one point, her daughter begged the mother to help end her pain: ‘She cried uncontrollably for 45 minutes. Sometimes she says ‘How do I stop crying Mummy? Help me, help me’
Concerned for her daughter’s future health, the unnamed mum told the court: ‘Unfortunately I know there will be more difficult times to come. Long term she will have to deal with the repercussions of her traumatic experiences for the rest of her life.’
The offender and half-brother to the daughter is currently on bail and is set to appear at Lewes Crown Court next month.