A Big Family (puzzle)

Another problem to kick off the week, once again adapted from Henry Dudeney:

Max, who already has some children from a prior marriage, marries the widow Wilma who also has some prior children. A dozen years later their family has a total of 12 children, including all prior children and the new ones resulting from their marriage. Each partner, Max and Wilma, have 9 children (out of the 12) that they are direct parents of.  How many children have been born to Max and Wilma together in the last 12 years?:
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.answer below

[...And alternatively, if you want a little meatier puzzle, Mike Lawler just walked his kids (and readers) through one from MIT yesterday: http://tinyurl.com/njkkepd ]
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ANSWER:  6 of their own  (having 3 each from prior marriages)