Basically, a woman I know at work told me today that even though she has known her husband 11 years and been married for 6, her parents and his have only met once. At the wedding. And even then they only spoke for a minute. Since the wedding 6 years ago, their parents have not seen each other again (Both set of parents are in their 60's, no facebook or twitter etc.) They literally do not know each other. My friend has met her husband's brother a number of times (and his wife and child,) and he has met hers. They meet maybe 3-6 times a year. But both sets of parents have met once in 11 years. At the wedding! They live just 15 miles apart! 
Another colleague of mine chipped and said she married her husband in 1993, after 7 years together, and their 2 sets of parents didn't know each other either. They met once during the 7 years before the wedding, then at the wedding, and once 2 years after at the first child's Christening. But then her husband's parents died close together, 3 years after they got married, and so the chance to meet again was gone then anyway. They also lived fairly closeby (the town next door - 20 miles away.)
So...... is it weird for the 2 sets of parents of a couple to have virtually nothing to do with each other? Or is it fairly common? What experiences do people here have? Do your parents have much to do with your partner's parents? And also, do they live close to one another?
Obviously if the 2 sets of parents are in different countries, then it wouldn't be unheard of for them to not have much to do with each other. But the parents of my colleague's (the one in my first paragraph,) and her husband's parents, only live 20 minutes drive from one another. Yet they have met once in 11 years! (My friend has no kids so there have been no Christening or childrens parties etc.)