Yes I have, but not all hens will lay a double yolk egg ever in their egg laying life. Some will lay a few double yolk eggs in their life. And outta all of the birds I have dealt with in my 20 plus years of having chickens, only one mixed hen laid double yolk eggs regularly. Even through she laid more double yolked eggs than she did a normal egg, she still didn't lay an egg everyday, not even as a new layer. And since she is now a few years old, she has really slowed down. She hasn't had as long of a egg laying life since she sent out all the doubles.Ok use your scientific logics. But what I am saying is the truth and I am not going any further than this. It is not imposible for a chicken to lay two eggs. haven't you ever heard of a double yoke egg? My friend had a guinea fowl that layed three to two eggs each time. She found it dead one day with it guts hanging out. She took it to the vet and explained how many the guinea layed and the vet told her that was the reason for it to die like that.
Because for a hen to lay a double yolk egg, they have a glitch in the egg formation process and two yolks get released to be formed into one egg shell. Which is why most double yolk eggs come from new layers who's bodies are still working things out. I personally look at it as the hen cheated me of the next day's egg, or from a hatching egg since double yolk eggs don't do so well as a hatching egg.
I think your friend either had a guinea that was slightly egg bound alot or being that it was a guinea......I'm not going there
It comes down to, it's hard to believe that one sumatra hen is popping out two whole eggs everyday much less 5 sumatra hens are popping out two whole eggs each everyday. As stated above no breed does this and its not possible to do everyday. So I guess I'm just going with Coop Scoop and you have other layers getting in and helping out