The short answer to that question is yes. However, if you receive the real estate as a result of it passing to you and your siblings at death you get the benefit of a "step up" in tax cost basis. This means that if you sell the property after her death (for example) for 250,000 and it was worth 210,000 at the moment of her death (date of death value), the capital gain would be $40,000. The proceeds would be split and the taxable capital gain would be split in the same proportions (I assume 25% each or $10,000). This is better than the option some families mistakenly fall into which is to have mom gift the real estate to you by deed prior to her death in which case the capital gain would likely be much greater (if she paid $100,000 for it year ago and it was sold after her death, as above, for $250,000 the capital gain wold be $150,000 split 4 ways).
Also, depending on her residency and the size of her estate, she may also have NJ estate tax issues. You may want to have her visit with an estate planning attorney where she resides to review these issues. I also am usually concerned with long-term care issues for the elderly and she should also have this issue reviewed.
This is not legal advice nor intended to create an attorney-client relationship. The information provided here is informational in nature only. This attorney may not be licensed in the jurisdiction which you have a question about so the answer could be only general in nature. Visit Steve Zelinger's website: http://www.stevenzelinger.com/
By "inherited" I presume you mean that it will pass as a bequest of her estate. If so, there is a "stepped-up" basis to the fair market value at the date of death. Presuming that the sale is at the FMV, then there would not be any gain. If your mother does not have a Will and Estate plan, she should definitely see a lawyer.
I hope this helps!
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Yes they are liable for whatever tax might be due. However, given IRC Section 1014, which "steps up" the basis in the property to the date of death fair market value, there is likely to be no tax due.