Random Chick-ery

Chickens can have twins, but not usually.  The first obstacle is the chance that both yolks are fertilized, one or the other may be but two would be rare.  If by chance both were viable then it is a matter of space. As they develop, quarters get cramped rather quickly. Then there is the air problem. When the single chick first pips, one of the things it gets is air, nice fresh air. It has been living on the air stored in the egg between membranes. Two chicks working hard, use that small amount of air up very quick. Egg shells are porous but two chicks competing for the same air as one would normally need is another obstacle, so they must be fast and break through the two membranes and the shell at record speed.  Mostly this means that in order for a chicken to have twins, they have to be very very lucky.

Still, it looks cool when you crack open an egg for breakfast and find two yolks.

Seriously.. Thoughts?