Wow. My heart goes out to the surviving siblings. This post is going to be rambly, so bear with me here.
The first thing I noticed was that all of the siblings had names starting with 'T'. All of the Turpins had 'J' names... This stuck out to me. It's probably just coincidence, but... Wow.
Also, if I'm not mistaken, one of the older siblings said that some of the other siblings were as thin and sickly as Tayla but 'grew out' of it. Makes me afraid that at least a few of the survivors were starved as babies and somehow managed to pull through (maybe until they didn't need a bottle).
Lastly, the speech impediments. This hits home for me because I still struggle with one to this day (mine is caused by a neurological issue). I started speech therapy early but my speech will never be completely 'normal', even though it got a lot better as I've gotten older. It just seems weird to me that all but one had speech impediments (if I remember correctly, nothing was stated about one of the older brothers having a speech impediment while all of the others were listed as such). Did the 'parents' not talk to them and they ended up picking up their speech patterns from their older siblings? I wonder if one of them (the oldest?) actually has a speech impediment caused by neurological problems or some sort of palate/jaw deformity and the others speak the way they do because they learned from their sibling. I think the second oldest is the one who doesn't have a speech impediment, so maybe the oldest two received some more attention from their parents.
Maybe I'm thinking way too hard about this. All speculation on my part, of course.