Dad went to ICU. There was a family meeting that my step sister and step mother never told me about. What can I do?

Everything Alva said.

I want to add that if this NH is permanent, then I hope your stepmom is doing everything by the book. If your Dad needs Medicaid down the line, there is a 5 year look back and any money that was Dads, at least 50% of the marital assets, better be intact. Because there will be penalties if money was given to his Sdaughter that could have been used towards his care. So dear Stepmom may be digging herself a hole she cannot get out of.

You may want to consult with an elder lawyer to see how Dad can be protected. May not be able to do anything because she is his wife. A Will will not even help at this point if Dad left anything to you and she spends it all before you inherit. Guess you would have to sue her at that time?

Your stepmother is married to her husband, your father. She likely has all rights to do as she is doing. She is likely the POA for your father. This means she can liquidate property for his costs now, and (unfortunately) may even be able to liquidate properties held by them both in order to spend down his funds in some way for future care. You cannot know what is legally going on here, and to be frank, your stepmom is now the wife. Unless your father put away funds in his name and yours, there is no way to insure you figure in any of this in any way. I would imagine your stepmom has legal advice on what she is legally able to do. Property doesn't get sold without someone having the right to sell it. If you want any legal investigations, if you suspect that this wife is purposely trying to undermine her own husband, you might wish to see an elder law attorney to see if there is any intervention you can do. However, I doubt it. Your father has remarried. He has not taken any and all aside to make a legal Trust that protects the children of his first marriage; that is too bad, but it is unlikely he can do it now at this point. These issues are the reason that such things are crucially important.
For now you are left with your Dad and your love for him, and a stepmom who is the lioness at the gate, who decides if you can even SEE your father. The important thing is yours and his relationship and your support of him now while he is ill. I would get along with all and leave matters of money and property to the side, as, in all frankness, it is too late now.

Is anyone the financial PoA for your father? If he was in ICU and incapacitated then the medical/financial PoA authority was most likely legitimately activated at that time. Also, there may be covid restrictions in place so that only 1 or 2 family can be in the ICU at a time. Are you local to your Dad and step-mom? Or do you live farther away?

Was your dad moved to nursing home for temporary rehab from his illness? Or is he now in long term care? Him being of "sound mind" is your non-medical opinion...has he had a cognitive exam? Often if an elder has recently had anesthesia it impacts their mental function afterwards, sometimes permanently.

Is your StepMIL's name on the title to the house or other properties? The financial PoA may be selling the house to pay for his care... you don't seem to know details for certain so I'm not sure there is anything you can do other than consult with an elder law attorney who specializes in elder abuse. This attorney will assess what evidence you have and decide if it is strong enough to pursue into court. You will be liable to pay the legal fees.

They may be making a huge mistake in selling his assets since this would most likely delay or disqualify him for Medicaid, should he need it. Again, consult an attorney -- that's the only person who can really help you in this situation.