The death certificate also stated Blackstock was cremated, and no autopsy was performed, according to People.
Blackstock and Clarkson, 43, got married in 2013 and were together until 2020 when Clarkson filed for divorce.
They shared two children: daughter River, 11, and son Remington, 9.
Blackstock became her manager after they began dating.
The pair engaged in multiple legal disputes during their acrimonious divorce.
In 2023, after the divorce was finalised, Blackstock was ordered to pay Clarkson US$2,6 million ($4,4 million) for breaching talent agency laws in respect of his management.
The lawsuit filed by the pop star claimed Blackstock secured her multiple deals and accepted generous fees in return, but as he was his then-wife’s manager at the time, it was against California laws.
An obituary released this week revealed the former talent manager was in a relationship with Clarkson’s former assistant at the time of his death.
In the obituary, the former assistant Brittney Marie Jones was described as his “beautiful and loving partner in life and business”.
Jones was referred to as Clarkson’s “former assistant” in documents for the couple’s rodeo business, The Daily Mail reported.
The timeline of the couple’s relationship is unclear, but it is known that Jones was previously married in 2021.
Shortly before Blackstock’s death, Clarkson cancelled the remaining shows in her Caesars Palace residency.
In the announcement, she referenced his illness and said she needed to be “fully present” for their children.
