Heinrich Thyssen-Bornemisza and Adoption
Thyssen-Bornemisza was born a commoner but married into the Hungarian aristocracy. After his marriage he had himself adopted by his mother-in-law (which made him technically his wife's brother) in order to inherit the family title. The Thyssen family fortune, one of the largest in Europe (estimated at $1.5 billion), is based on steel-making, but also includes glass, plastics, auto parts, shipping, trading, precision metal works, agricultural machines and information systems, and they were one of the principal users of slave labor under the Nazis.
He began one of the world's greatest art collections, primarily of European painting from the 12th to the 18th centuries. His heiress and grand-daughter, Franzisca, married Karl Habsburg, heir to the throne of the Austro-Hungarian empire, in 1993.
Millar, Peter. "Austrian Royalty Rages against 'Vulgar' Bride: Karl Habsburg and Franzisca Thyssen-Bornemisza," The Times [London], 31 January 1993, p. 1/16