Thierry Roussel: Inside His Business Life and Onassis Family Connection

Introduction

Thierry Rousselis a French businessman best known as Christina Onassis’s fourth husband and Athina Onassis’s father. His business interests include the Swiss family office SGFC, where company records list him as a board member as of September 2026.

His story reaches beyond that marriage. It also includes years spent helping administer his daughter’s inheritance, followed by a court-ordered change in how that estate was managed.

Quick Facts

The birth month and nationality appear in French corporate records. His business role and family history are detailed below.

A Background in Family Wealth

Roussel came from a French pharmaceutical family. That background helps explain why financial reporting describes him as a pharmaceutical heir.

But family background tells only part of the story. His own documented business connections include investment management and property-related companies.

The professional database Preqin identifies SGFC as his private investment office. It classifies the organisation as a single-family office, meaning it handles the financial interests of one family.

His Business Connection to SGFC

SGFC’s full name is Société de Gestion Financière et Commerciale SA. The Swiss company was entered in the commercial register on 2 June 1987.

Its registered activities cover financial and administrative services, along with property work. These records offer a firmer picture of his business interests than descriptions based only on his family’s wealth.

The company remains active. As of 7 September 2026, register information published by Moneyhouse lists Roussel as a board member and authorised signatory.

That wording has a specific meaning. It confirms a formal company role, without making assumptions about the work he handles each day.

Marriage to Christina Onassis

The couple married on 17 March 1984. Christina was the daughter of Greek shipping businessman Aristotle Onassis, and this was her fourth marriage.

Their daughter arrived the following year. Athina was born on 29 January 1985, according to contemporary Associated Press reporting.

The marriage later ended in divorce. Christina died in 1988, leaving Athina as her only child and heir.

That changed the family’s future.

Roussel became closely involved in his daughter’s upbringing, while the administration of her inheritance placed him in a separate and demanding position.

Athina’s Childhood and His Later Family

After her mother’s death, Athina grew up with her father and Gaby Landhage, alongside her half-siblings.

Roussel and Gaby’s religious wedding took place in Villeny, France, on 12 May 1990. Athina attended the ceremony, an event documented in an Associated Press photograph.

He and Gaby have three publicly documented children: Erik, Sandrine and Johanna. Together with Athina, that makes four children.

A Vanity Fair account of Athina’s childhood describes Gaby’s involvement in raising her alongside the other children.

The Dispute Over Athina’s Inheritance

The inheritance brought serious disagreements.

After Christina’s death, a five-person board supervised the estate she left to Athina. Roussel served alongside four longstanding business associates of Aristotle Onassis.

The administrators disagreed over its management. Their dispute became a major part of the public reporting surrounding the family.

In 1999, a court-ordered transfer placed administration of Athina’s fortune with the Swiss auditing firm KPMG Fides, as described by ABC News.

The distinction matters here. Helping administer an inheritance does not make that inheritance the administrator’s personal property. Athina was the beneficiary of her mother’s estate.

The management change also needs careful wording. By itself, it does not establish financial wrongdoing.

His Public Interview

Roussel addressed criticism publicly.

In 1998, he sat for an interview with Diane Sawyer about his business background and his handling of Athina’s inheritance. He denied accusations concerning business failures and spending from the estate.

Forbes later reported on that interview, including his responses. It remains a documented example of him speaking about issues that had drawn attention to the family.

Final Thought

Roussel’s public story is closely tied to Christina and Athina Onassis. Yet his registered business connections provide another part of the picture.

The clearest account keeps those roles distinct: a father involved in his daughter’s upbringing, a former estate administrator and a businessman with a documented SGFC board position. Each is supported by a different part of the public record.

FAQs

Who is he best known as?

He is best known as Christina Onassis’s fourth husband and the father of their daughter, Athina.

What is his nationality?

Thierry Roussel is French. French corporate records confirm his nationality.

What does he do?

Thierry Roussel is a businessman connected to the Swiss family office SGFC. As of September 2026, register-derived information lists him as a board member and authorised signatory.

When did he marry Christina Onassis?

They married on 17 March 1984. Their daughter Athina was born in January 1985.

Who did he marry after Christina?

Thierry Roussel married Gaby Landhage. An Associated Press photograph documents their religious wedding on 12 May 1990.

How many children does he have?

Thierry Roussel has four publicly documented children: Athina, Erik, Sandrine and Johanna.

Did he manage Athina’s inheritance?

Thierry Roussel served on the five-person board supervising her inherited estate. Administration was transferred to KPMG Fides in 1999.

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