Allegations of sexual assault by an heir to a beer fortune against his own older brother have thrust one of Thailand’s richest families into an uncomfortable spotlight, stunning a public unaccustomed to seeing prominent households air their affairs in public.

The scandal erupted last week when Siranudh Scott, better known as “Psi” – a fourth generation heir to the Bhirombhakdi family’s beer-to-real estate empire – shared allegations of historic sexual abuse by his older brother, Sunit, on Instagram.

In an emotional video released on May 9, followed by audio recordings purportedly capturing the two brothers discussing allegations dating back to their teenage years, the 29-year-old environmental activist said he no longer wanted to be known as the “Singha heir” – a reference to the family’s market-leading lager.

“Everyone in my family knows it because they listened to the tape I recorded of his confession,” he said of the allegations. “I don’t want to stay in a family that does not value me or have empathy for me.”

Sunit has denied the allegations. In his own social media video he acknowledged bullying his younger brother during trips home from boarding school in the UK, but flatly denied any sexual abuse, calling the claims “disgusting and awful”.

Psi, an open-water swimmer widely known to the Thai public as “aquaman” or “merman” for his marine conservation work, followed up this week with a prime-time appearance on the talk show Hone-Krasae. The episode, which has since racked up 2.4 million views on YouTube, featured Psi tearfully describing his estrangement from parts of his family.