Let me try try to explina in a different light. The other posts are correct in the teachings of the catholic church and marriage/sexual relationships. I noticed that you brought up the age of mary in your OP. When comparing cultures it is vastly important to understand the reasoning behind both cultural acceptance of morals. In Jesus’s time and before and after, indeed in some countries today, it is morally acceptable for a very young child (12-15) to marry. This oft times correlates to the average age of the population as well as other health factors. Since most girls go trhough puberty around 12-13 if not younger it means that there bodies are becoming ready to give birth. Their hips are widening, their ovaries are producing eggs correctly, their hormone levels are ready to support pregnancy. Most men do not reach this stage of being able to reproduce children until their late teens, hence why older men would marry young girls, because even if two 12 year olds marry, the boy would not be able to fullfill his sexual intimacy with his wife at such an early age, thus it would not be until years later that the marriage would be real (with the sexual act done) and childbearing would be delayed. In those cultures most times child mortality is high, another reason for the concept of “go forth and multiply” alot. Lots of pregnancies would equal a greater chance of surviving children. With one woman she can really only have one child a year (barring multiples), plus recovery and the natural BC that breastfeeding provides.
Since children were so desired in those cultures it was not uncommon to divorce or to quickly find a young wife after the death of a spouse, to try again to produce more children. Women also have a somewhat limited time to healthily produce children, generally between 15-25 (at that time or in those cultures). We do not have problem and women can give birth in their 30s and 40s (though in those later yeards health complications are greater) Men can keep reproducing almost until they die, baring erectile disfunction. So a man with no sons, or surviving children in his 50s would marry a young girl of 13 so that he could get the maximum amount of years with her to produce more children. Again this is a cultural thing mainly to do with survival of the family or the blood line.
In America, as other cultures today, women on average live about 89 years. Infant and maternal mortality rate is also much lower than other cultures or times. Thus it is perfectly feasible for a woman to have twi pregnancies that result in two healthy surviving adult children to go on and reproduce. Part of the reason why maternal and fetal mortality rates are low is that we frown upon activities that increase those chances, such as children very very early on, and even later on in life. Another reason is that we understand the human brain more and know that the comprehension section does not fully develop until the late teens, thus ability to make adult rational decisions after carefully examining the potential consequences, something that young teenagers do not have.
We also are not forced to have teenagers work for their livelihood at such a young age as we used to. They are not responsible for whoel countries, villages, towns, castles and their occupants etc. such as the medieval ages where it was not uncommon in the most to have the lord of the keep being only 15, making the decisions for that land much like a mini king.
I hope that this enlightens you a little more.
