To make this as accurate as possible, I first analyzed the faces of my parents. What are their signs of the ageing process? For instance the ears; they've become significantly larger if you look at my father. However, the ears of my mother didn't increase in size. Based on my resemblance with both of them I estimated what the effect would be on my aging signs. 
Below are three sketches which I made to analyze the proportions, and the original photograph in which I'm 21 years old. (In the year 2040 I'll be 48/49)