The present age of Mohan is \(\frac{{19}}{{17}}{\rm{th}}\) of the present age of his brother and the ages of his sister is \(\frac{{23}}{{17}}{\rm{th}}\) of the present age Mohan’s brother. After 6 years, the ratio of ages of Mohan' sister and his age is 13 : 11. Then, what is the age of Mohan’s sister after 8 years?