If you want to see your kid become independent, you should make them before you reach 47

If you do not want kids, do not make them.

If you just want to make a kid and not worry about seeing them growing up, you can make them at any age (when it is still possible).

If you want to pass your life experience to your kid, see how they implement what you taught them and become independent (at least 18 years old), while still being in your mind, you should make them before you reach 47. That is because most diseases related to the brain are likely to start occurring from the age of 65. These diseases can change one’s personality or even kill them. If you are sure that you will be fresh all the time you are alive, then the maximum age to have a kid would be: life expectancy for your country and gender minus 18 years.

It is all about probabilities, which does not allow us to make any predictions about a particular person. However, given that the information on a death age and an age of brain diseases is unknown for an individual, the most reliable information we have is probabilities. Here are sources that support this conclusion:

First of all, it is important to mention that mental skills start to decline on average from the age of 45. However, this decline is relatively weak: around 10% decline by the age of 65 compared to 45.

Source:

“The findings also reveal that over the 10-year study period there was a 3.6% decline in mental reasoning in men aged 45-49 and a 9.6% decline in those aged 65-70. The corresponding figures for women were 3.6% and 7.4%.”

https://www.bmj.com/press-releases/2012/01/05/cognitive-decline-can-begin-early-age-45-warn-experts#:~:text=The%20brain's%20capacity%20for%20memory,published%20on%20bmj.com%20today.

Alzheimer disease often affects people older than 65.

Source:

https://www.hopkinsmedicine.org/health/conditions-and-diseases/alzheimers-disease/stages-of-alzheimer-disease#:~:text=Alzheimer%20disease%20usually%20affects%20people,people%20and%20slowly%20in%20others.

The majority of strokes often occur in people who are also older than 65

Source:

https://stanfordhealthcare.org/content/dam/SHC/clinics/stroke-center/docs/stroke-young-patients-qa.pdf

The chance of having a stroke around doubles every 10 years after age 55.

Source:

https://www.cdc.gov/stroke/risk_factors.htm#:~:text=The%20chance%20of%20having%20a,65%20years%20also%20have%20strokes.&text=In%20fact%2C%20about%20one%20in,adults%20ages%2015%20to%2049.

“Average age at the first heart attack was 65.6 years for males and 72.0 years for females.”

Source: