The quick answer is no, he can’t. Texas has a statute that says that a devise or bequest of property in a will to the attorney who prepares or supervises the preparation of the will or to an heir or employee of the attorney is void. This statute applies to anyone who is not related to the attorney. The attorney can be a beneficiary of his family's wills even if he prepares it.
In a recent case, an attorney had a woman working in his office that was an independent contractor. She was not an employee of the attorney. She was a paralegal but she just did occasional work for the attorney. She also did occasional work for other attorneys who shared office space with the attorney who drafted the will. The will made her a beneficiary and also appointed her as the executor of the will.
A sister of the testator contested the provisions of the will leaving part of the estate to the paralegal. The court agreed with the sister and ordered the paralegal to return all of the property that she had received to the heirs of the testator. The court also ordered the paralegal to pay the attorney fees of the sister.
The paralegal appealed claiming that the statute did not apply to her since she was not an employee. The appeals court denied her appeal and held that the gift to the paralegal was void. Jones v Krown.