An 18th-century painting long considered lost has been found in the home of a California lawyer whose family had held the piece for generations but was unaware of its origins.

The painting, lauded as a masterpiece of colonial Mexican art depicting mixed-race families of the era, has been acquired by the Los Angeles County Museum of Art (LACMA).

Museum curator Ilona Katzew said the painting was one of two missing pieces from a set of 16 painted by Miguel Cabrera, a master portraitist in high demand in the religious and social elite of New Spain, a Spanish territory that included what is now Mexico.