The appointment sits above everyone
The priority order in § 711.002 begins with a person designated in a written instrument signed by the decedent. Only if no such designation exists does the order fall to the surviving spouse, then adult children, then parents, then siblings. A valid written appointment therefore displaces the entire family sequence.
That is a strong instrument, and it is under-used because most people assume a will covers it. It generally does not, in time — see below.
Who should make one
Anyone whose closest relative by law is not the person they would actually choose. Separated but not divorced. Estranged from an adult child who nonetheless sits above a devoted sibling. A long unmarried partnership, which the statute does not recognise at all. A blended family where the children of a first marriage and a second spouse are unlikely to agree.
Also anyone whose wishes are specific — a particular tradition, a scattering location, a refusal of embalming — and who wants those carried out by someone who will actually do it.
Why a will is usually too late
A will is located, read and often probated after disposition decisions have been made. Cremation frequently happens within a week; a will may not be looked at for a month. Instructions about a body belong in an instrument that exists separately and is findable immediately.
Give a copy to the person you appointed, keep one where it will be found, and tell your family it exists. An appointment nobody can find on the day it is needed is the same as no appointment.
What to include
The person you appoint and how to reach them, plus an alternate. Whether you want cremation or burial. Any tradition-specific requirement. What you want done with cremated remains, if anything. And your signature, dated, with whatever witnessing formality the form you use calls for.
This is a document worth having a Texas attorney prepare or review, particularly where family conflict is genuinely expected. Nothing on this page is legal advice.