Twin hatching

[Midwestmomma]

I have a twin at day 16. Why do most die? It seems like many die close to hatch day are they too weak to get out or? If they have individual yoke then I don't understand why the die later in incubation but before pip.
I'm trying to cram on this and be prepared in case one survives and needs help.
Any input appreciated!

 

[nuthatched]

Because there's not enough room in the egg for both to reach good size or for both to pip.