Two brothers have gone on trial accused of raping and abusing their younger sister who was four at the time of the first alleged attack.
The boys, aged 15 and 13, live in Birmingham and cannot be named.
At the city's crown court they denied charges of rape and sexually assaulting the girl, now seven, between September 2006 and May 2009.
The older brother has also denied sexually assaulting another sister who is now 10.
Prosecuting, Mark Heywood told the court: "The prosecution case, in a nutshell, is that each of these two boys sexually abused their sister... and, in the case of the eldest, abused his other sister as well."
In a recorded police interview shown to the jury the alleged rape victim was seen playing with a toy train as she described what happened to her.
The girl told the officer one brother had assaulted her 15 times and the other brother had assaulted her at least 10 times.
The 15-year-old is charged with two counts of rape and four counts of sexual assault of a child. His brother is charged with two counts of rape and two counts of sexual assault of a child.
Neither boy was made to sit in the dock during the opening of the case and instead sat with their grandparents.
The trial continues.