You're unfortunately leaving out part of the equation. Did your mother die with a will in place or intestate? It sounds like you might be making assumptions about what rights you and your siblings have to the property. How and to whom the property passes will greatly affect the answer. Please provide some additional detail.
If you find this answer useful, please mark it as "Helpful". Likewise, if you believe it is the most responsive, please mark it as the "Best Answer". The information provided herein is for informational purposes only, and should not be relied upon or construed as legal advice or legal opinion. You should not rely upon the information provided at this site without seeking individual advice from an attorney. No attorney-client relationship can be assumed or created by this post.
You may have to probate the Estate.
I am a former federal and State prosecutor and now handle criminal defense and personal injury/civil rights cases. Feel free to check out my web site and contact me at (212) 577-9797 or via email at Eric@RothsteinLawNY.com. I was named to the Super Lawyers list as one of the top attorneys in New York for 2012. No more than 5 percent of the lawyers in the state are selected by Super Lawyers. The above answer is for informational purposes only and not meant as legal advice.
If she died without a will (or "Intestate") and your mother was not married at the time of her death, you four children can execute a deed basically saying: "you, brother, sister and sister, as the sole surviving heirs of the Estate of Mom" convey the property to "brother" - and you can do this without the considerable time and expense of Administering your mother's estate or seeking judicial approval.
That said, you and your siblings seem to be acting very generously. You are giving up what may be a valuable asset, for no consideration. If you are all convinced that you wish to do this, you should speak to a Real Estate attorney. This can be done relatively easily and inexpensively.
You should have your mother's estate probated (if she left a will) or administered (if she didn't leave a will). Then the sisters could give the property to the brother if that is their desire.
Although it is possible to do this without getting the courts involved by just having the sisters execute a deed in favor of the brother (as the sole heirs or devisees of the mother) the title that your brother would get would always be questioned. It is better to have the court give it's approval, thereby ensuring that your brother's title would be clear and insurable. It is important when he wants to sell or refinance the property.
Note: This response is for general informational purposes only. No attorney-client relationship is created. No responsiblity shall be taken by the submitting attorney for any individuals acting pursuant to any information contained herein.