did not sign the deed? Do I own this 1/2 Acre of Land?
My mother is now deceased and I have other siblings! What does that change?
The deed is binding against the interest your father owned in the land. I assume that your parents also reside in the State of Texas. Texas is a community property state, so unless your parents have entered into an agreement to separate their respective interests in this property, your mother would still own one half interest in the property, making you and your mother tenants in common. You do have certain rights as well as duties in dealing with the property when you share ownership in this manner.
This answer is provided for general information only and does not constitute legal advice pursuant to an attorney-client relationship. If you cannot negotiate with your mother to acquire her interest in the property, you would be well advised to discuss the matter with a local real estate attorney who can advise you as to dealing with the property (paying taxes, using as a residence, renting out, etc.).
Re Additional Information -
Mother's death means that her one-half share would pass either (1) under her will (if she died with a will) to the beneficiaries named in the will or (2) via intestacy (dying without a will) to her heirs-at-law. If you are a beneficiary under the will, you may be able to work with the Executor and the other beneficiaries of the will to trade for the other half of this property in lieu of other bequests to you. May be handled via a Family Settlement Agreement. You otherwise would have to buy out the beneficiary(ies) that receive the interest or otherwise remain as tenants in common with each of them on a prorata basis.
If your mother died without a will, same would generally apply as to the heirs-at-law. Probate would be handled differently in an intestacy situation.
You need a wills, trust and estate attorney for assistance in negotiating for the other half and a real estate attorney to advise re rights and responsibilities as to ownership as a tenant in common (if you are unable to negotiate to acquire the other half). You should be able to deal with one attorney who handles both types of law as they are related areas of law.
There are responsibilities associated with the upkeep, maintenance and taxes on the property that need to be handled on an ongoing basis. If you are unable to acquire the remainder, you need to know how to handle with the people who succeed in interest to your mother's half. Assuming it is a valuable piece of property, you don't want to not maintain it or pay the taxes and have it lost to a tax or maintenance lien. That doesn't benefit anyone.
Again, this is informational in nature as I cannot render legal advice in this forum and with limited facts. Hope it helps point you in the right direction.