Then I followed the links. This livejournal post is about Jeffs' community. It's bad stuff, which I have mentioned before on this blog, I just forgot his name.
What it boils down to this this - they practise polygamy (EDITED to clarify - in fact polygyny, men have multiple wives, women have one husband). Children are home-schooled and have no contact with the world outside the cult. When girl children reach a 'suitable' age (like 13) they are married off to the old guys who run the cult. Teenage boys are surplus to requirements, some are sent away, and live homeless in places like Los Angeles. it is possible that some have 'accidents'.
Quote from that livejournal post (linked above)
One disturbing thing which I hadn't come across in my readings before, but which
has apparently come to light in the last year, is the existance of the
"Babyland" graveyard. Here are the quick statistics on
it: 425 graves, 6 entirely unmarked child graves, 227 child
graves all together for a total of 53% children under 10, A high number of
children suffering from strange accidents. A disproportionate number of children
"run over". A number of children who have just
"disappeared". The death rate is particularly high among boy children, ages
From across an ocean I can't comment on the plausibility of this. There is a news report from New Zealand about the child graveyard here, and an (admittedly one-sided) letter to the FBI with allegations about the deaths here.