I proof-read for all of my family: my husband is moderately dyslexic but writes match reports for his rugby club every week, which go on the club website, so it's good to be accurate. He also wrote a book, and I checked all that, but was only shown the text, not the photo captions: after the book was published, there it was, sticking out like a sore thumb, under one of the pictures - Rhodydendrons! That's probably because that is how all of his family pronounce the name of said plant!
My kids too, although now well into adulthood, still ask me to read over anything important they have written: they went through school at a time when being over-strict with spelling, punctuation and grammar was frowned upon as suppressing their freedom of expression and creativity!
My mother was a teacher of English and made sure all my SPG was correct!