is it ilegal for a 20 something to have sex with a 13 year old girl with her parents knowledge? if so what is the penalty?

Any sexual penetration with a person under the age of 16 is a felony in Michigan, including intercourse, oral sex, fingering, etc., is a felony in Michigan, punishable by up to 15 years in prison. Because the age difference is more than 5 years, any sexual contact (e.g. fondling of the breasts or buttocks) is a misdemeanor, carrying a maximum of a two years sentence. Parental knowledge is irrelevant, but if it can be shown that the parents aided or encouraged the sexual acts to occur, they too can be charged.