Per court documents obtained by PEOPLE, Heche's older son Homer Laffoon (whom she shared with ex-husband Coleman Laffoon) has filed a nine-page supplement to his previous petition to assume control over his mother's estate.
The 20-year-old claims that his mother's ex James Tupper, 57, has been interfering with Homer's attempts to communicate with his 13-year-old old half-brother Atlas Heche Tupper since Heche's death in August.
Homer also claims in the filing that a 2011 document Tupper considers a will — and which he asserts named him administrator of Heche's estate — is not valid because the signature on the document does not belong to Heche and was not observed by two witnesses as required by law.
Legal representative for both Homer and Tupper did not immediately return PEOPLE's request for comment.
JC Olivera/Getty; Anne Heche/Instagram
Per Tuesday's filing: "Mr. Tupper repeatedly refers to the email attached to the Objection as a 'will.' However — as a matter of law — the email does not qualify as either a holographic will or formal witnessed will," the document reads. "The email fails to satisfy the legal requirements for a valid holographic will because the material provisions of the purported will are not in the handwriting of the Decedent. A will is valid as a holographic will, whether or not it is witnessed, if the signature and the material provisions are in the handwriting of the testator."
The filing continues, "The email presented to the Court as Decedent's 'will' by Mr. Tupper fails to meet the requirements for a valid holographic will because the signature and material provisions are not in the handwriting of the Decedent. The email fails to satisfy the legal requirements for a valid formal witnessed will because the email was not signed by the Decedent and does not have two witnesses who signed the document during the lifetime of the Decedent."
The document also points out that without a proper will, "there can be no nomination of an executor" or an executor selected, in general. This role is important as the executor "is appointed to administer an estate pursuant to a valid will," according to the legal papers.
Homer also called several of Tupper's own previously filed objections to the 20-year-old's "suitability" to administer his mother's estate — including claims Homer was "'estranged' from his mother at the time of her death" — "inaccurate and unfounded."
Axelle/Bauer-Griffin/FilmMagic Anne Heche
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Heche was involved in a fiery car accident on Aug. 5 and then was transported to a Los Angeles-area hospital. The actress sustained several injuries from the incident, and PEOPLE confirmed two days later that she was in a coma and had "not regained consciousness" since the crash.
The state of California declared Heche legally dead on Aug. 12, but she temporarily remained on life support to allow for her organs to be removed and donated. On Aug. 14, her rep confirmed to PEOPLE she had been taken off of life support.
She is buried at the Hollywood Forever Cemetery in Los Angeles.