Has anyone had experience with financial changes after hospitalization? Possible undue influence on an estate?

Thank you for your reply. Here is some additional background.
Our family business was sold in the mid 80s, making him very wealthy. Dad was divorced and married again in 89 with his wife dying less than 2 years later. He remarried his current wife in 95, I believe. Prior to this, I was co-owner of his properties and business affairs. I married in 94.
Dad was always somewhat of a playboy...handsome, wealthy, and he lived well on the North Bay Road in Miami. His current wife began to see him prior to his 2nd wife;s passing and was roughly 25 years younger. From the beginning, she began to demand things be taken out of my name and put into her name, despite the matters being totally disconnected from her.
Dad was never loyal, and ran around regularly on his 3rd wife and paid her rent and a monthly fee of around 3-5 thousand/month. Dad also provided me roughly 2 thousand and insurance coverage as well. I regularly visited dad in Florida 4 or 5 times a year, including my wife and daughter. Soon after he married #3, I was no longer welcome to his home in Florida at the insistence of his wife. This became the norm over the next 20 years as it became increasingly difficult to talk to him. His wife was recording his phone calls and would berate him 24/7 for anything he would do that she didn't approve. He had told relatives that he was afraid of her at times and told me several times that he had made a mistake but was too far in to do anything about it.
When we sold our family business, we had an agreement and a promise that I would never have to worry about anything, as there was close to 30 million to draw upon. Millions of dollars of insurance was purchased to offset the inheritance taxes I would need to pay someday and it was common knowledge that this was to be my inheritance. An irrevocable trust was created and the insurance policies were put into it, but nothing else. Everything was fine until dad was hospitalized and his wife discovered the payments to his other women, as well as my distributions, which she knew about and it bothered her greatly. His wife took control of the finances due to dads hospitalizations and poor vision. His wife made him discontinue the payments to his girlfriend(s) and also myself. He came up to where I live and he resided part time without telling me...I live 3 miles away. He sold his home and properties, business interests, and everything else without telling anyone, myself included. He then called me, with his wife in the background, and told me he was low on money and needed his remaining money to provide a residence for his wife. I would rec'v no inheritance other than the insurance. Because the insurance was in an irrevocable trust, it couldn't be taken out of my name like the rest of the properties and business interests. Instead the premiums were allowed to expire and the policies had to be sold for a few pennies on the dollar. In the end, everything that had been promised and arranged was suddenly taken away after decades of it being the norm. He recently liquidated everything for a few more million, while claiming to be broke, living in Old Palm Beach in a gated community and paying $50K/year for country club dues.
I wouldn't be so bitter but this was promised to me and suddenly, now that he is dependant on her an she does the finances, his behavior is quite different than 18 months ago. His wife has always known aout his girlfriends, but now that he is getting elderly, she is tying up all loose ends.
ts not like I want all of his money. I am his only heir and now I am totallly cut out of everything, while his wife, who was allegedly a professional prostitute, gets everything. I only wanted enough to live without worrying where my next meal is coming from. I'm trying to live on $25K/Year on disability. Anyhow..thats my story. Am I wrong for wanting something out of my 60 years?

Thank you for your reply. I don't argue about most of what you say, but I am far from a spoiled rich child. Prior to his 3rd wife, we sold our family business for 10s of millions. From the proceeds, I was provided an income and insurance coverage with the promise that I would not have to worry again. He also provided incomes for at least one girl friend for a similar period of time, with the same promises. Everything was fine until his wife took over the finances and has vowed from the day she married that she would get his money.
Its not that I want all of his money, but I am his sole heir and he has told me and others that he has made a mistake but is afraid of her and now is totally dependent on her.
It is more than a simple issue with not getting along with my step mother...I was promised in the mid 80s that the proceeds from the business sale would be my inheritance, and this was well known and basically a verbal contract. Now, within the last 18 months that he has allowed he to take oveer the finances, all of his properties, business interests, and everything else has been liquidated and put into her name.
All this going to a girl who he met at the race track, who was known as a probable professional prostitute. I hate to be bitter, but I'm trying to live on $25K/year with a family while they live in Palm Beach, paying 50K in club dues annually.
As I mentioned, this isn't a simple issue and all of this was said and done long before she came into the picture. I'm looking for an attorney that might know of some way to prove that she has coerced him to act in a way that he would not typically behave.He also had 60 years to change things around...is it a coincidence that all of this happens once she takes over the banking?