I discussed marriage age in an earlier post. You may run into couples marrying at 14-16. It's rare, but it does happen. I honestly think that this is more likely in certain regions of the country than in others. Hill or mountain families may fit the profile better than city or farm folk. If you have a parent born about 1605 with a child born about 1620, become very suspicious and investigate. You may have siblings or half-siblings rather than parent/child.
 Parents tended to have large families well into the 20th century. Child mortality due to disease and other factors played a role. The need for help on farms [boys generally tending to plowing and other chores; girls to household duties] or the family business also figured in to the mix.
 Multiple marriages led to large families as well. A widowed father needed a wife to look after his children. A widowed mother needed a bread winner to provide for her children. A widower with three kids might marry a widow with four of her own. They might add 2-3 children of their own. Now you had a family with 9 or 10 youngsters.
 Back to the large family issue for a moment. Say a couple married at 22 and had their first child at 24 and the youngest at 40. By the time the eldest children were of marriageable age, the youngest would be old enough to take over the chores of those leaving the nest.
 Families also might "indenture" their children to another family member or neighbor. If the older children were going to inherit the bulk of the family property, placing a boy with a local tradesman to learn his business would help guarantee the boy's future. A daughter might be indentured to a family to help with children, learn housekeeping, cooking or some other skill.
More on indenture next time!