@centrox,
Two individuals may be the same real age at differing ages. There are established numerous physiological markers for age/real age/extent of change in the direction of one`s demise. We are currently still using an arbitrary unit for this measure for change/ageing/our age, and this unit is time. Whist time measures the time it takes to orbit the sun we actually owe this unit of measure nothing whatsoever in relation to our aging. We have used it for want of a superior measure.
Whilst it may be possible, just, for a 29 yr old to be nineteen, so in real terms, (taken from an average for those of nineteen years), it may also be possible, or something approaching it, in reverse, for a nineteen year old to be twenty nine. I t is likely not so exceptional for such a couple, 19 yrs and 29 yrs respec to meet in the middle, to both be around the mid twenties, and far less so within five years. Whilst it is true that we are currently only herd animals I believe that this concept of real age is only just around the corner.
Your father whilst having been alive thirteen years longer might quite realistically have finished up twenty or more years younger. Thirty years, when viewed under the microscope, has been seen to be the absolute limit.