We 
were in Saint John the other day and ran in a couple who attracted attention because they were strolling around with their (6 month) twins. One woman (after telling the couple that she was fascinated with twins because her mother was part of a fraternal twin1) offered to make a family photo of the couple and kids.
From the twin’s parents, I found out that the boys were fraternal twins. Currently, the parents said that they could only tell the difference because one of the boys had more hair than the other. Other details were exchanged but before we laughingly parted, I advised the parents of the fact that ‘(when they get older) twins will be forming a block against you. Good luck’.
Very much needed so. I know from experience.
1 Obviously, the lady missed out on the fact that there were twins occupying a park bench, right in front of her. On the other hand, adult twins are less interesting than baby-twins.