Re: I'm also wondering ...
Well, I think she’s lost believability by having two sets of twins in the story already. If you have one rare thing happening in your story you probably shouldn’t keep adding on to the rarities. Having two sets of living twins much less two sets of twins period would also be rare.
It wasn’t unusual to name stillborn babies necessarily. I have many in my family line in the 1800s that were named (one had 5 stillborns sons with the same name...the fathers name). Although I would say it was rare since when you walk through a cemetery most are named “Baby Smith” or “Son of Mr and Mrs Smith” for example.