A YouGov poll put 18-24 year olds as 75% Remain. 25-49 56% Remain. 50-64 44% Remain. 65+ 39% remain.
I don't know what the turnouts were across each group - we also know YouGov have been getting it wrong lately.
There are certainly more older voters than younger, because our country has an ageing population. That's why we need immigration - to pay for the pensions of the old, and the benefits of those unable to work.