no such thing as free healthcare as a visiting relative
'anyone who comes to the UK on holiday or for a short term visit will have to pay for any NHS hospital treatment they may need while they are here, unless they meet the criteria for one of the exemptions from charges. This includes people coming to visit relatives who are ordinarily resident in the UK. Their entitlement to free treatment does not extend to you, even if you are going to be staying with them for several weeks or months. If you think you will have to pay for treatment, you are strongly advised to take out health insurance before you travel.'
http://www.dh.gov.uk/en/Healthcare/E...able/DH_074387
they should definitely have good health insurance if any family or friends visit you.