"My brother had power of attorney for my mom from 2000 until 2007. He had my mother sign a life estate deed with all three names: my name and his, and her name on it. I have power of attorney for my mother now since my brother died in 2007. My brother's surviving wife went down and filed for half the house. My mother is angry. She wants me to have the house since I am the only child left. My mom wants to revoke the deed."
o "My brother had power of attorney for my mom from 2000 until 2007. He had my mother sign a life estate deed ..." If your mother herself signed the deed it is not clear what relevance the power of attorney is. Did your mother sign the deed or did your brother sign as her agent? This might be important.
o "...with all three names: my name and his, and her name on it." This is a crucial fact to determine the result and the pertinent facts are not clear from your question. You really need a real estate lawyer in your state to review the exact language in the deed to determine who owns what. How were the names listed? It could have been your mother as a life estate with you and your brother as owners. If there was no indication as to the legal relationship as to you and your brother, than state law might govern to interpret the deed (i.e., to provide a default provision as to ownership). It could have been your mother retaining a life estate, and you and your brother as tenants in common. This latter phrase means that if your brother died he could bequeath his 1/2 share of the remainder interest (i.e., the ownership interest after your mom's life estate ends) to anyone he wanted, such as his surviving wife. If it was tenants in common and your brother had no will, then state law (intestacy) would govern, and likely your brother's wife would take some or all of the remainder interest (and estate attorney could help you decipher that issue). If the deed instead read that your mother had a life estate and you and your brother, as joint tenants with right of survivorship (JTWROS) owned the remainder interest, then in fact your brother's death would mean you would be the sole owner of the remainder interest, not your sister-in-law.
o "I have power of attorney for my mother now since my brother died in 2007." If the deed was already signed your holding a power of attorney may not mean much. If your mother is not able or competent to hire a lawyer to pursue this issue then you could do so as her agent under her power of attorney. However, it will look rather self serving (and might raise issues of a conflict of interest for you) if you as agent are trying to get the house, etc.
o "My brother's surviving wife went down and filed for half the house. My mother is angry. She wants me to have the house since I am the only child left. " It's not clear what your sister in law did. It sounds like your mother is still alive. So if it was a deed with a retained life estate in your mother, then you and your sister in law don't have any current interests in the property. What exactly did your sister in law file?
o "My mom wants to revoke the deed." The first issue is to figure out exactly what the deed said and who owns what. As discussed above there are a number of points that are not clear in this regard. So first, have a real estate attorney in your area sort out the ownership. It is possible you may not have any problem. If the deed does not accomplish what you want, then you need to determine what if anything can be done. This will depend on a host of factors including local state law, what the deed says, your families actions subsequent to signing the deed. You should ask a local real estate attorney if it is possible to revoke a deed based on mistake --- that your mother intended a different result (if in fact that is the case) and a mistake was made in signing the deed that left 1/2 the house to your sister in law. The lawyer might have some other theories to overturn the deed. Perhaps it was not properly signed or recorded. There may be some technical flaw in the deed itself or how it was processed/filed that would permit a change. However, this is a highly technical issue that will require local real estate counsel. If that type of position is to be taken then a challenge from the sister in law sounds likely.
What does your mom's will (and/or living trust) say? If your mom left all assets 50/50 to the two of you (so that if one of you died the other inherits all) then that would support your argument. However, if your mom's will left all assets to you and your brother outright with no trust it might be inferred that she was aware of the fact that you and your brother could leave assets to anyone. If that was the case that might contradict your position in that your mother could have prevented your late brother from leaving assets to his wife, but that she did not in fact do so. Many facts are missing.
You could have a really simple and quickly resolved situation with the result you want, or depending on the facts, you could have a legal mess that might end up in litigation if it is not resolved appropriately. Get some professional help, but gather copies of all documents and summarize all facts before you meet so that the attorney will be able to best help you.