One periodically sees the suggestion that medieval parents did not love their children. This ridiculous and patently false notion is based on the fact that the rate of childhood mortality was substantially higher than it is now, and the assumption that parents therefore must have become callous to childhood deaths.
In fact medieval sources are full of parental laments for dead children. Those who could afford it would make substantial gifts to churches to benefit the souls of their children. If the choice was to be callous or be sad a lot, parents went for being sad a lot.
(After all, our primate relatives, monkeys, apes, lemurs, mourn for dead infants. It would be bizarre if humans didn't. For that matter, childhood mortality rates in the US were substantially higher before WW II than they are now, and yet no one says twentieth-century parents didn't love their children.)
Childhood was however looked at rather differently than it is now, and, by our standards, kids had to grow up fast. Even though exact ages were not nearly as important for medieval people as they are for us, and no one had birthday parties, there was a sense that one's childhood was divided into 7-year sections.
Up until age 7 one was an infant, below the age of reason, not yet knowing wrong from right. Children were baptized at birth, because everyone agreed that the unbaptized went to Hell (baptism wiped away original sin, which otherwise would send you there), and they thus needed godparents, who would act for the infant. From 7 to 14 one was a child, knowing wrong from right but not legally able to enter into binding agreements or give oaths.
"Youth" set in at age 14. One was not fully an adult, but one could get married, give legal consent, and the like. It was convenient that this was the age of puberty, more or less. (Modern puberty shows up earlier, doubtless due both to our substantial diet and to hormones in the water.)
The age of 7 (or so) would be the age at which boys might start knighthood training (see more here), or be sent off to a monastery (see more here). The age of 14 (or so) would be when boys might head off to the university (see more here). Boys and girls who had grown up in a monastery would take their final vows not long after they turned 14.
We treat 21 as the age of majority, of full adulthood. It is the only age we have left from the medieval configuration, but, curiously, it was much less important for them than it is for us. "Youth" might continue for boys until they were in their 30s and ready to settle down, if a young knight went on Crusade or enjoyed the tournament circuit while waiting to inherit. Or "youth" might be over substantially earlier for someone who married in her teens.
Certainly teenagers (a recently coined word) were assumed to be much more responsible then than they are now. Young men routinely went off to fight, and Joan of Arc was in her teens when her visions told her to free France from English domination (which she then did). Among the peasantry, children would be helping farm from the time they were tiny--as is still the case among the modern Amish.
(Click here for more on medieval life expectancy.)