They are not uncommon but they are usually sorted out when they are candled before being sold to the general public. The double yoked eggs are used for industrial purposes.

thats a common enough occurance ,,,such eggs are slightly larger in size but sold at 1 1/2 times the prices

I've seen it a few times before

I eat 4 eggs everyday and get about 1 of those a year

That’s good luck

you killed 2 birds with 1 crack!

They are fairly common if you buy jumbos