Warning it's long!
My 6 year old ID twins have moderate to severe learning disabilities but L is streets ahead of G in terms of cognitive abilities, learning and communication.
We've spoken to our geneticist who says that ID twins can have significantly different abilities but that there must be a medical/environmental reason, unfortunately we have no idea what that reason is!
They were both v poorly when little, G more than L and we understand why that's affected her emotional development but don't understand why G's cognition is so hugely different (unless she suffered some brain damage when she had a respiratory arrest when tiny which is a horrendous thought)
I'd love to know if anyone else has ID twins with significant differences in ability. We want to do everything we can to help G achieve her full potential and stop her getting so frustrated. I also want to know how much of a pushy, pain in the arse mum I should be when asking for further assessments (we've already asked for a lot!) 
Thanks for reading, sorry it's long! Xxx