There are two questions here:
a) How to deal with on an individual basis? Which is largely case-by-case, and
b) How to deal with it on a social or political level?
We have dealt with many cases of family breakdowns caused by the Brahma Kumaris. It is what they do. Indeed, many of us here were ourselves agents of family breakdowns inspired and directed by the Brahma Kumaris. And the truth is, the Brahma Kumaris very much do give specific instructions and advice on how to break families up to their adherents, on top of a highly repetitive brainwashing that constantly portrays them as impure, ignorant and even evil.
BKs having difficulties with non-BK family members, or wanting to know what to with their wealth and assets, will go at first to center-in-charges and then the top leaders to be given personal instructions based on decades worth of experience in successfully doing so.
Therefore, you get the slow drip effect, and the sudden, mortal strike effect.
My first advice to any family in your situation is to act quickly and quietly, with as little discussion as possible, and put as much of the family wealth and assets outside of the reach of the Brahma Kumari banksters (money men/gangsters). Put it into a trust, put it into the names of grandchildren, give it to charity ... do anything but let it feed the Brahma Kumaris ambitions and real estate fund.
Don't be noble, don't think you are doing this "just for the money", you are doing a service to society but not allowing it to go to feed the hungry ghosts within the BKs. Think and act like at the level the BKs do.
In your specific case, I would be worried about the element of "undue influence" - a legal term for a power party knowingly exploiting a weaker vulnerable party - due to your Father's illness and your mother's dependency on him, that they are now sniffing around.
What often happens is, eg, the BKs get the family money and home on the promise of providing a shelter for the widow on the husband's death ... and then the widow becomes an unpaid servant for the cult in her own old home. The home becoming a BK centre ... because for a home to become a BK centre is - they claim - "the highest seva or karma".
They appeal to greed of the individual promising that b giving to them, followers will reap multi-million fold karmic return and liberation in life ... whereas if they give to their family, or non-BK charity, they would only be dragged down and entangled. It would be negative karma they would have to pay off by suffering.
The BKs will, of course, not want to look after your Father and mother in old age on a practical level. That will likely remain the family's or society's job and expense.
What can we do at a social or political level?
That's a more difficult question. The BKWSU has millions of dollars annual income, and a highly centralised structure, dedicated to PR (political and public relationships) and corrupting the media. They invest hugely into 'advance damage limitation', succouring police, security services, media and political parties etc with free gifts, free retreats, free courses, free rakhis etc ... of course they are buying favours in advance to make it harder for the truth to spread.
For me, it is easier to innoculate a non-BK *before* they become infected with BKism. Once an individual is infected with BKism, it is like a drug addiction or fever that you pretty much have to let run its course and waiting until they themselves wake up, or sober up, or have a bad enough experience in order to choose to leave themselves.
Then it's just a question of being there to take them back *on the condition* that it is one family (the real family) or the other (the so called BK "family").
Therefore, as with alcoholics or drug addicts, it's just a question of not-enabling or encouraging their habit.
If you had a junky or alcoholic in the house, you would not leave your purse with money lying around, you'd hide it because you know they would steal it and spend it on drugs or alcohol. So to with BKism.
Each of us who has suffered - or sobered up - has to decide what and how much we can afford to do warning others about BKism and obstructing its infectation of our societies. Just a little bit whenever you can contacting others and so on ...
Unfortunately, BKism is not enough of a problem any more to alert government or society. They have learnt to keep a low profile. The abusers, although involving crores and suicides etc, are relatively low level in comparison to terrorism etc. It is not a whacky enough cult.
However, the lastest chapter with Virendra Dev Dixit and the AIVV shows it is possible.
If I were you I'd contact the NGOs involved and attempt to get them to spread their investigation wider to involved the BKs as well as the PBKs. Two peas in the same pod.
Then all you can do is keep warning others at whatever chance you can to create awareness and consensus.
Specifically in your case though, allow me to repeat that the more advanced your Father's health case become, the gret the legal case of undue influence arises and it might be an area of 'undue influence' and 'power of attorney' where a family lawyer might become involved.
Something else to consider is gently lobbying your entire family and any of their friends who have been effected and together confronting them with the damage or effect they are having. "Confront" is too strong a word ... appealing to them, reminding them of the good times, how much they shared, how much they are valued, offers of help etc.
But don't allow the addict to start preaching BKism and make any offer of help conditional, the BKs or us. If they choose the BKs, then - I would say - leave the BKs to look after when they get old.
Ask them to make it clear ... will the BKs look after you when you get old? Unless they have and give a lot of money, the answer is no. Only the very inner circle is looked after. We've many cases where they have dumped back on families or left for society to look after, eg social housing.
BKism teaches individuals to cut off mentally, emotional and physically from their family and loved ones. Utterly. 100%. Non-BKs are impure and evil. Non-BK values are impure and evil. Theirs is a black and white world which they are at the top of and everyone else below them. Ignorant and dangerous.