Keisha Bolton and Wilco Van Kleef are the worlds tallest married couple according to the Guiness Book of World Records(2009, see update). Keisha met Wilco searching for a dance partner through the UK Tall Person's Club, and they married in 2001.
An article about the couple here
My Comments: There were some reports that another couple was taller than the Van Kleef's but I can't find that info.
Update: A couple in California, the Hallquists, have now been named the world's tallest couple by Guiness.