US population 300 million

lets say if 1 out of 10 are left handed and there are twice as many left handed men
30 million = 20 million men and 10 million women

56% of 18 yr old or older Americans are married
160 million= 80 million men and 80 million women

16 million married people are left handed
11 million men 5 million women

therefore the odds are 1 out of 4,389 that both partners are left handed

I am a statistician and the question is not that difficult.

The assumptions that you made are:

1 in 10 married people are lefthanded
Twice as many married men are lefthanded than married women

In order to meet those two assumptions, the odds of a married man being lefthanded would be 2/15 and a married woman being left handed 1/15. (Taken together that gives you 3 out of 30 married people being lefthanded, which is the same as 1 out of 10.)

So, if a random selection of one male and one female were made, the probability that they were both lefthanded would be 2/15 times 1/15, which is 2/225, or 1 out of 112.5.

I'm not a statistician. I didn't know what to do with the numbers. I do know a lot of people. Until today, I didn't know any that both husband and wife were left handed. Go figure.