In about 40 years of raising pigeons, I've only found one set of twins in an unhatched egg. There may have been more, but I only opened the one and found the two embryos. However, by the time I'd found them they were partly decomposed so I just trashed them. Recently, I received these photos from Steve Shaw. Despite what I posted originally, these are NOT triplets. The third youngster shown is from the second egg. I don't know whether the twins are fraternal or identical.
Here's what he said about these: "This egg started to pip and was alive when I first checked them. There was a second egg that hatched and is doing fine. The next day no progress had been made so I opened it. This pair has had a perfect track record."
Most twins never make it out of the egg. They simply die in the shell. There seems to be no way for them to turn enough to crack the shell and escape at hatch time. I do remember one person telling me many years ago that he was able to open the shell and allow both twins to hatch and they did fine, growing into healthy adults, but in the normal course of events twins simply die. The photos below are courtesy of Steve Shaw and I think they're great.
