I intended no dig at you or your relatives (tho timed after your post I'd posted before seeing it)- I taught for nearly 40 yrs (& come from a teaching family) - my own take on the rapid growth in dyslexia is that it had some connection with the change in teaching of English to primary school children some 25-30 years go (away from the phonetic to the word recognition) - this appears now to have been accepted as a significant contribution to the dysfunctional literacy now seen in many adults.
It always surprises me to see the level of understanding needed to read the Manx press of the 1880's which had a very wide readership (and the Primitive Methodist journals which were definitely aimed at the non-affluent end of society where schooling was minimal) as compared to today's newspapers aimed at the same stratum. I'm happy to take up the topic off-line with you if you wish.