Another point to consider is that the researchers appear to be looking only at first marriages. The divorce rate for people who have multiple “marriages” is likely higher.
In my own family, between my wife’s and my siblings, there are a total of nine siblings, 13 marriages, and five divorces. That’s a divorce rate of nearly 40%. But among the nine siblings, there are only two persons who have been divorced at all. That’s 22%. Of eight first marriages, there were two that ended in divorce. That’s 25%.
There are 5 siblings between my family and my husband’s. Of the 5, only one marriage has survived. (My husband’s brother has been divorced twice and married 3 times, don’t know how you figure that.)
The only marriage that has stayed together is ours, and if we make it till December we will be married for 57 years.
Your family's experience illustrates an important point. In constructing divorce statistics, you can count the fraction of all marriages that end in divorce or you can count the number of ever-married people who are or have been divorced. The former will give a larger fraction because divorced people who remarry are more likely to divorce again. A good website is http://nationalmarriageproject.org/