Hi Slinky. You need a letter from the doctor regarding your mum and sister's conditions. This might cost you about �20. You should contact your travel agent, or whoever you booked with, telephone in the first place, explain the situation, that you are not in a position to take the holiday, and then send them the letter from the doctor to confirm the reason. As the 22nd May is quite close now, and the situation is one that you could not possibly have forseen, they might be sympathetic, as Paraffin says. As the time is short for them to re-allocate the accommodation, they may offer you something. It should say something about what happens in such an eventuality somewhere on your booking form. Good luck. Schutz.