Police in Lethbridge say they investigated after receiving information last month that a boy was engaging in sexual activity with his 10- and eight-year-old sisters.
The boy, who cannot be identified because of his age, is charged with incest, sexual assault, sexual interference and invitation to sexual touching.
He has been released from custody with the condition that he not be in the presence of anyone under 12 unless an adult is present.
The boy made his first appearance in youth court last week.
The matter was adjourned to Aug. 27.
Police say no further information will be released.