Crackers, sorry to hear your dads family turned their backs because they believed someones lies!
I can totally relate though, as my mum and dad split when I was young, and he eventually got together with this woman who never had any kids and so put alot of pressure on me and my brother to be very family-ish when we were there!
Anyway, she was basically a bit of a fruit cake and seemed mainly interested in my dad for money, he didnt have much, but if she could get out of paying the bills etc she would!
When he got terminally ill about 3 years ago, she never did anything to encourage him to seek medical help, she didnt look after him when he couldnt look after himself (so I had to whilst doing my degree, alone because I was the nearest family) and then she tried to get involved with applying for his benefits and stuff, and he refused and told me he didnt want her involved because she was a money grabber etc.
She was so pissed off with this she just upped and left him totally, and then the night before he died, turned up at the house and starting looking all over for money and telling him she would be glad when he was dead and it turned out had been telling him for months I was only caring for him because I wanted his money!!!! How horrible! (he actually didnt have any money to his name, dont think she knew that!) He died the next day, my family arranged the whole funeral and were incredibly civil towards her because we knew she was basically batty and unstable. But afterwards, because I didnt stay in touch (obviously) even though I was polite and never said anyhting nasty to her about her actions, she went round telling everyone laods of lies and horrible stuff about me, and wouldnt let her be involved in the funeral arrangments etc even though she didnt want to!
Families eh, who have em!! Haha!! xx