so about £6k a year - less in Liverpool (but both Unis haven't published figures for 19)
This is confusing - the maintenance loan they get isn’t dependant on which uni they go to - unless they are in London or living at home.
So assuming you are in England and both are away from home, they should both get exactly the same - and this will depend on your household income if over 25k. It is different if you live in another part of UK I think.
So if that works out at 6k, then both will get that amount.
In theory you should top it up to the maximum amount (which is currently £8700)
In practice it depends what their costs are.
DS was in Liverpool, got min loan of £3821 in first year, we added £1420 to cover his rent, then gave him £300 per month, for 8.5 months (mid Sept to end May) so in total he got just under 8k, which was more than enough for him to live on. He did have a retail job for part of year but saved his earnings.
Second year, his house rental was cheaper, so we needed to top up only £200. We gave him more monthly, so it worked out that he got just over 7k in total, but again he had plenty to live on as rent was low.