I would try and contact them for an explantion, over and over if necessary. They could have been listening to gossip regarding what you have said or done which is totally untrue. I know its up to them to believe or not believe rumours, but sometimes things are taken at face value and cause rifts.
If it had not been for my sister who rightly confronted me me about what my mother was saying I had said about her and my brother-totally untrue and we now know the reasons behind it- I would have been estranged from them for years.