There can be other advantages or reasons for a will. So while nothing in your post tells me there is a reason for your parent to make one, I'd want to ask more questions to determine what planning is (and is not) necessary.
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Yes, your parent still a Will even if you are not aware of any need for it at the moment. Why? Because, you never know for sure what will come up that may require an estate administration. For example, the government may provide a benefit to the estate, etc. In this case, you can either have a well done Will to make the process simple and inexpensive or your parent can go naked and end up having the family deal with much more in hassle and expense. Why play it risky when a well done Will solves the potential future problem.
I would suggest that your parent go and speak with an attorney so that the attorney may review their entire situation. In general it is always best to have a will. Just because there is no conflict now does not mean there will not be one later.
I agree with my colleagues that a Will is seldom a bad idea. I would only point out that, under the facts as stated, a Will is unlikely to ever be used. A Will only governs and controls probate assets. If all of the assets are jointly held or have beneficiaries designated, then there would be no need to open an estate, and the assets in question would also bypass a Will.
It is a good idea to meet with an estate planning attorney, anyway, because there are other estate planning documents needed, even if your parent decides a Will is not. For example, your parent should have a durable power of attorney for financial and medical matters. This will eliminate the need for guardianship/conservatorship proceedings in probate, if your parent ever becomes incapacitated.
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