The language thing is interesting.
I'm not a good speller but I have dyslexia as well - and they're often co-morbid.
I can see the children are similar they can't "hear" all the sounds in words - means the sound it out method as well having mutliple options of letter combinations I also miss or mishear the sounds.
I had speach therapy when younger - possibly verbal dyspraxia - Mum can't remember and I was too young to know.
Our children haven't had that though I did have concerns with DS at nursury as did reception teahcers but speech therapist were unresourced and he wasn't bad enough and they thought he might improve with age - which he did.
Spelling was a list of random letters till I started teaching the kids spelling and was teaching patterns form structured programs - done outside of school as help in school was often patchy and variable quality if they got on it al all - SENCO at first primary blocked DS and DD1 getting help for a few years despite class teachers insisting they needed it.
My vocabulary was always huge and I think I was always making links with other words and meanings. I do wonder if a structured approach to spelling would have help me have fewer problems rather than emergent spelling which was in vouge at the time.
DD1 teachers have mentioned she very good at linking information form different sources - I think DS is too quiet for them to be aware of him doing it.
The kids spelling is mixed - DD1 is poorer than expected for someone with her ablities despite us going through several programs - which I'd started earlier with her. DS who struggled most and couldn't rely on memory as much as sisters is now by far the best speller and DD2 is just okay.
I'm not great at languages - but younger two especially DS seem to be and I think that's thanks to duolingo - labguage app they do every day - I think little and often practise seems to really suit them.
I think it's again getting things into long term memory.