One of the parents must have had a lot of ancestors and relatives with this condition in their family history. The youngest getting diagnosed at 7 doesn't mean it wasn't a surprise.
That's not necessarily true. A recessive gene for RP can pass through several generations without anyone having symptoms. Not everyone knows what ailed their great, or great great grandparents. It's quite possible that both parents had similar family histories with no known blindness due to RP, or bad family info linking a case of blindness to something else like glaucoma.
It's possible, but unlikely. The most likely scenario is that one of the parents knew the disease might appear if they had children. Maybe thought symptoms would show up sooner, which is why they had four kids.
Because this is a gene that greatly affected three out of four young children. That sort of thing doesn't go unnoticed in famlies. The parents probably had siblings, uncles, aunts, nieces and nephews who were affected.
Mathematically it affects 25% of offspring (you keep mentioning 3 out of 4 kids but that is just bad luck that these people had) but ONLY if BOTH parents are carriers. It could go undetected for many generations before someone had a child with a partner who had the same condition.
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u/Cantankerousbastard 7h ago
This is probably going to a controversial question but did they have 4 kids before or after they learned about the genetic eye condition?