I have a breeding pair of pekin ducks and buff orpington. My buff drake has been breeding both females and vise versa with the pekin drake. My pekin hen lays an unusual amount of double yolkers. Now she is not a very broody girl but my buff is. To give her a good full clutch, I took the liberty of adding a few more eggs. She was happy to have them. About 6 of the eggs I gave her were double yolkers. I know this by the size of the eggs. I am wondering first what the chance of survival for twins is and two, how rare is it for my pekin to be laying double yolkers about twice a week. Would it have anything to do with her being breed buy both breeds drakes?