I agree with Attorney Webb. It sounds like that your position as an heir is not in doubt, but that of other possible heirs. So, if there are funds that will be distributed, you should be able to find an attorney that will step in, particularly since there are not any filing fees left to incur. Push hard to find a qualified attorney. Be prepared to demonstrate that there will be funds from which the attorney can be paid.
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You would need to open up a probated and ask the judge to order DNA testing to determine heirship before the Court had any authority to do so.
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If there is money or other assets in the estate, you should have no problem finding an attorney to represent you. If you are questioning paternity, you need an attorney.
There is obviously an underlying estate action open. You should not attempt to handle this on your own.