Dear Isaac56,
Welcome to the Forum. You have found the right place for most diabetic answers and also a very friendly bunch of 'diabetics' as well who will be pleased to help you.
The first thing I would say to you is simply 'dont worry unduly' diabetes isn't the 'killer disease' that it once was and by educating yourself about diabetes you will then have the key to taming this condition. Yes you do run an increased risk of developing Type 2 diabetes alongside your father and brother who as you say, already have this condition, but if you care to search through this site and take note of the excellent advice and the practical information in the various postings to a whole range of questions, you will find out what are real practical answers.
Take things one day at a time, the IGT by itself dosen't necessciarly show that you are diabetic, and it might at this stage be only showing that you haven't quite got there yet, which you should take as a good warning sign to revise your diet/exercise/lifestyle and possibly avoided becoming diabetic altogether.