27 so 40 I guess?
I think maybe higher if we have the same end goals and they look younger than their age. Some people look younger than they are and some older; my sister's fiance looks 20 years older because of the facial features and height difference but they are only 5 years apart
As for younger as long as we look not too far apart

and their level of maturity is enough then maybe like 20 as youngest.