Four children died separately in their late teens - why?

Market Drayton Cemetery, Market Drayton, Shropshire
(Click on an image for a larger version)
A medium sized gem with lots of interesting finds and some curious features such as the twin chapel with a central arch that "by order" should only be approached by a hearse driven in reverse gear.
There must be an interesting story behind the age at death of the various Burgess children. Four of them died in their 18th or 19th year which to me suggests that they all had some inherited genetic disorder.

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