An alternative to mothers maiden name?
If the "families" around here are anything to go by, they'd be better (and more secure) to start asking for the fathers name. Guessing that would take far more than three goes. I'd wager that some of the mothers no longer know, if ever they did.
I still recall a news clip from way back in the 80's when the Tories were looking at single parent benefits and a woman, sweeping her arm across her four kids, says "I don't receive a penny from any of their fathers."