I want to clarify a few things before I take a stab at this answer. New Jersey was not "settled" by Europeans in the early 17th century. There was a small settlement founded in 1630 called Pavonia, but it was extremely small and was actually settled by the Dutch. An entire section of (modern day) New Jersey became a colony of New Sweden shortly there after, however in 1664, England was able to requisition full control of the region. It really wasn't until decades later that waves of immigration took place on New Jersey's shores. If you want someone in your story to have immigrated here early, your options will be more limited. Massachusetts, Virginia, and Maryland are among the colonies that were more heavily populated early (you could potentially always have the families relocate from another colony to New Jersey).

Were divorces and/or second marriages common?

These are two completely different concepts. Divorces were extremely uncommon across all religions and all areas of the colonies during the 17th 18th century. You would have to go hunting through records to find examples of this since they almost certainly never happened, at least not with any regularity.

Second marriages happened in the event that one spouse died. This was extremely common for women, who, through the concept of coverture had no rights and were essentially the legal property of their husbands. If their husband died, they could (and often would) lose land, titles, and other social standings without a husband. This could be rectified if the couple had a son who could inherit from his father. Still, many women, especially younger women would remarry in the event of an unexpectedly young death. On the flip side, men would at times remarry, especially if they had not yet had children, especially male children.

How many children did they usually had?

Very hard to answer broadly through the course of the 17th century. Many families gave birth many times, but that was because childhood mortality rates were incredibly low. 12% of all white children in the 18th century would die before they were one year old. 25% of all children would die before reaching the age of 10. However, if you reached the age of 10, you were much more likely to survive until at least the age of 37. This meant that families felt the need to reproduce more rapidly since children often died young and families wanted to have as many descendants as possible. It's difficult to give you a 'typical' range because that's really an open ended question. A typical number often cited is that the average married family had at least five children, however, at least one or more would not live to see their adolescence.

What was the normal age to get married for men and women?

Depends. Things were very haphazard in 17th century Americas. Populations were small. Law and order was not always present. Societal necessities, like doctors weren't always present. I tried finding a source for 17th century marriage rates and simply couldn't find a reliable one (my main area of expertise is the 18th century, So to try and help, I'll post that). Marriages for young men were typically in their mid-twenties and for women usually early twenties. However, courting for young ladies usually began in the mid teen years, usually around 16. Women could get married as young as 16, but that was uncommon. Most parents had their children wait until at least they were 18 - 20 at the earliest. Sometimes there were execptions which could include unplanned pregnancies or if a wealthy family predicted their own financial perl on the horizon, they would try and marry off their daughters early, to reputable families before their doom was at hand.

Hope this helps. Let me know if you have follow ups.