What happens if a homeowner dies and the house was not listed in their Will?

Check the will. If the will mentions the residue of the estate as all personal and real property not included in the specific provisions from the other portions of the will, then it may very well still be in the will. Second, if you have siblings, you need to check to see how the title to the home was listed; was it listed as only her on the title or did she include any particular sibling on the title with her and how. If the will discusses residue, then you and your siblings need to bring this property up in the probate matter and figure out how you wish it to be handled before you present it to the court. Either way, most likely what will occur is the property will be considered to be owned by all of you as tenants in common, with equal percentages for each.

I am so sorry for your loss.   This question is best asked to an attorney in your area that can read the Will that has been written.  It is quite possible that the house will fall under the residuary clause in the will : "the rest residue and remainder " of the estate paragraph. Who receives all the residue in your Mom's Will?  It really all depends on how the Will was written.  Generally if your will omits a residuary clause then the assets that are not mentioned will pass to the heirs by intestate succession (i.e., via the intestacy laws in your state).  If that is the case here then you as siblings will probably share equally and then yes, you would have to buy them out of the house.  Good luck.