"I assume that his closest relatives would assume ownership of the domain."
That's not a certain assumption by any means. It might depend on what country the registrant was living in, what was the TLD and registrar, whether he left a will, and whether the law of the relevant jurisdiction recognizes a domain name registration as a descendable (by intestacy) or devisable (by will) asset.
In the case of a .com domain name, for example, the registrar MAY have a policy in place to deal with deceased registrants, or the registrar may not. In the absence of such a policy, it is by no means certain that the registrar would recognize what amounts to a transfer of the domain name by, for example, a will.
There is a silly debate over whether domain names are "property", which has something of the air of a religious debate, and is just as irrelevant to most real world issues. There is no one right or interest known as "property". We use the word "property" to refer to a grab bag of various rights and interests that one might have in something. (for the longer version of this rant, see
http://www.open-rsc.org/essays/berryhill/property/ )
Most registrars take the position that a domain name registration is a personal service contract between the registrar and the registrant, and is non-assignable. While practically all registrars will permit a novation of that contract (i.e. where a new party assumes the prior party's place), you will note that most .com registration contracts have an express non-assignability clause. The reason for this clause is to prevent registrars from becoming involved in bankruptcy, contract, or, yes, probate disputes with persons other than the one who registered the domain name.
Let's say, for example, that your dead registrant had registered the domain name for use in a business where he is a partner with someone else, and that the business has accrued a trademark interest in the domain name. I would imagine that the partner would be quite surprised indeed to find out that the domain name, which had been registered and used as a joint asset of the partnership, is suddenly the subject of claims from the registrant's heirs. It is precisely this kind of problem which the registrars seek to avoid in the non-assignability clause of the domain name registration contract.
To give another example, let's say your registrant had not died, but instead had gone bankrupt. Do the registrant's creditors obtain possession of the domain name as they would any other assets of the registrant? The State of Virginia says they do not.
Before you begin negotiating with people who may or may not be at all relevant to whether you can obtain registration of the domain name, you will first want to consider the law of the jurisdiction where this person passed away, the law of the jurisdiction of the registrar, and whether the registrar has any specific policies for dealing with this kind of situation. Even in the absence of a specific registrar policy, the executor or administrator of the estate may be able to get away with requesting a modification of the domain registration and provide a copy of the appropriate court document granting or recognizing the administrative powers of the executor. But before you sign a check made out to anyone, you had better be certain that person is in practical control of the domain name, even if the legal situation is unclear.
