I believe she has been subtly influencing him against us for a long time and I don't know how to handle it or what to do. There were many small instances over a long period of time that made me start to feel concerned that this was happening, but it was hard to pin down - the overall picture was worrying, but very hard to call out any one thing and I kept thinking that maybe I was imagining it.
It culminated two years ago when I was told, very unexpectedly, by text that they wished to have no further contact with us. The text was from my Dad's phone but I have reason to believe it was not written by him (the language and phrasing used, plus her habit of sending messages 'as him' from his phone previously) and I was then blocked on all our contact channels. It happened as they were about to move house. They subsequently moved and I wasn't given the new address.
I know that she and her adult children persuaded my Dad to sell his house and changed his power of attorney to her child. So I think some of this may be money/inheritance motivated. I also think she just doesn't like me very much. I was always friendly and polite to her when I saw her but we were clearly very different in character and so were not particularly close. She would only ever talk about herself and showed no interest in any of us, she was very judgmental and would gossip constantly about people we didn't know and tell us all the feuds she was having with people. I was never rude to her, but I'm sure she was aware that I wasn't warming to this; I didn't give her gossip the oxygen she wanted.
However, that being said, I was glad that my Dad was happy in his relationship with her after a bereavement and a period of being alone. I genuinely wished the best for them. Now, my children miss them both immensely and I feel so sad to have lost him from my life, but am also worried about him and angry that she seems to have manoeuvred things so that it doesn't seem to be possible for me to contact him without her intervening, and impossible for me to regain a relationship with him.
She is a very strong dominant character and my dad is very submissive in relationships. He does have previous form for being heavily influenced by dominant individuals (including one instance which resulted in him cutting other close family members out of his life for years under their influence, which he later retracted on). However, my Dad and I had always had a good relationship and he seemed to adore my children.
I don't know what I can do. They are always together. There doesn't seem to be any way I can get in touch with him without her intercepting or preventing it. I have heard, from other family members who are still in a small degree of contact with them, that she has been saying things about me that are not true, and if he is believing those things it is unlikely he will want to get in touch with me. Does anyone have any advice?