I have three sets of relatives who were all born on the same day and are/were married to each other - my grandparents (both dead), and two sets of aunts and uncles (ie. my aunts have the same birthdate as their husbands).

Only my granparents weren't born in the same town, the others were.

Not as unlikely as it would seem.

It's great fun when my neighbours snag my wi-fi then download movies all night on it, reducing my browsing speed to a crawl.