Multiple yolked egg are not conjoined, they develop into separate embryos for the most part@aart I know. It would be cool to see if they would be conjoined triplets or just triplets. I had conjoined twins and I didn't even know tell I cracked the egg open.
Very, very few have made it hatch.
Here's a search here for double yolked hatches:
https://www.backyardchickens.com/se...]=1&c[nodes][0]=5&c[title_only]=1&o=relevance