Incest by children under the age of 18 years

I found a daughter of my co-wife who is 17 years old having sexual intercourse with my son who is 15 years old. I reported the incident to the Police for them to charge the girl with the offence of having prohibited sexual relationship with my son because she is older than my son. To my surprise, Police refused to charge the girl on the ground she is under 18 years and cannot commit prohibited sexual intercourse of incest. Does this mean girls under 18 are allowed to sexually abuse boys who are younger than them?
LK Tabora

The Police are right. Under section 160 of the Penal Code which establishes the offence of incest by females, only females of or above the age 18 years can commit the offence of incest by female. While a girl under 18 cannot commit incest by female, a boy under 18 years, can by virtue of section 158 of the Penal Code, commit the offence of incest by male. The age of a boy can only be relevant in assessing the proper sentence to be imposed when he is found guilty of the offence but for girls, their age determines their capacity to commit the offence of incest by female. This means your son who is younger than her sister can be prosecuted for incest by male but his sister who is 17 years cannot be prosecuted for the offence of incest by female even if she is the one who might have incited the boy to have sexual intercourse with her.