How does a contingency lawyer work?

I might consult with an Estate/probate attorney. The Administrator/Executor of the estate is required to represent the deceased person's estate properly and that might include a claim for wrongful death, if applicable. I'd ask for advice on ensuring your brother is doing that and pursuing the claim. If he isn't, I'd ask for remedies to make it happen.

Out of curiosity what’s driving you to want to do a lawsuit?
I’d be concerned that unless it’s something extraordinary that happened, life value after a certain point is kinda nil. US Life expectancy overall 78 yrs & 81 women & 76 men. There’s probably an algorithm to deduct each chronic diseases. We have a friend 72, who has had melanoma, diabetes, heart issues & smokes.... he’s jokes that his stats have him already dead.

Now if they died related to a disease with settlement funding to compensate, that’s different. Like mesothelioma.

@igloo572 Thank you...this helps alot. My parent was young (70s) and my sibling won't talk at all...so it's hard...my parent had no minors as children. The attorney I'm speaking with wants me to sign a contract first...I actually haven't spoken with the attorney...just the office...they are very professional and capable but I could be stuck with a bill if my sibling starts there own case...so it's a catch 22.

I’m assuming this is a medical malpractice atty & if so my experience is that they have an RN on staff who does the initial review of case to evaluate. Evaluation done before any litigation actually filed. (As an aside on this, actuarial tables are used to determine life expectancy, & will be used in determining amount of settlement.) If these are the steps for this atty, I’d suggest you try to get the contract & fees divided into 2 parts: the review phase and then litigation phase with a total out allowed IF once you discuss review / evaluation phase you stop any further action.

Also find out before you do this IF lawsuit will likely pay out to your parents “Estate of”. Not to you or your sibling. If it pays to “Estate of” that snowballs into having to have probate open or probate continues to stay open with asset / debt filing updated as every settlement check comes in. If probate already open, whomever is named executor must be involved & aware of lawsuit being considered as they &/or the probate atty represent the Estate and deal with any assets (like settlement $) of estate. It sounds like executor will be / is your sister and your relationship is less than ideal so this can be a real problem. $ received means updated probate docket work to be done. This will have time needed & costs..... please pause to think how all this might work between you and your sibling. Executor has a good bit of discretion as to just how they do distribution, if executor wants to s...l...o...w  walk distribution, they can. 

Often a single sum settlement is done as most do not want to leave probate open ended. Whomever your suing knows that and if you want single sum settlement, it will likely be for less $. Could decrease payout significantly. Less $ for atty as well. Read contract if there’s a separate fee or charge added to the % contingency fee for single sum settlement. 

Please, If you do not understand the contract have another atty review it for you.

Out of curiosity, your parent were they relatively young when they died & did they leave behind dependents (not heirs but minors or handicapped dependents)?

It sounds like the contract specifies that you will have to pay if you don't continue with the case. Does it spell out how they will determine the charges? If not, you should ask that before you sign anything.

BTW, your sib's POA status is not valid once your mother died.