My brother is 21 and lives at home with our mum he is unemployed after dropping out of uni twice. He received very basic student loan whilst at uni as my mum is a high earner, I think around 3k a year for the two years he attended. However he had no end of holidays, went to Malia for 4 months and Zante for 4 months (he claimed he was working but with hinds sight think that was a lie), Amsterdam, will only wear designer labels, has the latest gadgets etc. He has never worked. He even has a 60inch TV on his wall which he told my mum he bought for £100 as it had a tiny scratch 
I live 300 miles away but went to my mums to visit last week. When I was at there I opened a letter for my brother thinking it was something else. It was from a debt recovery firm requesting payment on behalf of Santander in the amount of £570. I assume its an overdraft or loan he hasn't paid. The letter said he had been contacted several times and needed to reply and set up a payment agreement. I didn't tell my mum about the the letter but I am worried.
If he doesn't pay the debt, which he won't he will just stick his head in the sand and hope it will magically disappear, can they go to my mums house to recover the debt, will this affect her/her credit?