Getting married at last minute is kinda rare here in Viet Nam unlike Japan and South Korea. We arent at that stage yet although the trend do seem to increase in the 3 largest city.
Girls and boys are urged by their family to marry early and raise babies quite soon. One of my female friend got married right after she graduate from high school and have her first child at 20. There are a few reason for this , in rural area , giving birth early is fundamental , as the sooner you raise your children the quicker they will help you as manpower ( agriculture and fishing require lots of physical work).
Getting married early may seem silly to some feminists , but it is quite wise to do so. The best age to perceive a healthy and strong child is around 22–25 , and at that time , you are still young enough to continue work and prepare money for when he grow up. Raising a child is very expensive , and postponing it will increase the cost a lot more due to extensive healthcare for the mother.
Me personally , i encourage most to get married at 24–26 , right after they finish college and start gaining job experience. Most should have their first child no later than 29 , because 30 is the magic age where women’s body start to change drastically ( although with proper habits and care , it would delay a lot ).
Family is very important here in Viet Nam like many Asia country, and 3 generation living together is not RARE.