Nicole Richie & Christina Ricci are not related. Nicole's birth name is Nicole Camille Escovedo.
Christina Ricci was the fourth child born to former model Sarah Murdoch and psychiatrist-turned-lawyer Ralph Ricci. Christina’s father is of half Italian and half Irish ancestry. Christina’s mother has Scots-Irish, and possibly other, ancestry.
Christina’s paternal grandfather was Victor Edward Ricci (the son of Henry Ricci and Valentina Fiorentino). Victor was born in New York, to Italian parents.
Her paternal grandmother was Charlotte Mae Ryan (the daughter of Patrick James Ryan and Helena J. Shay). Charlotte was born in New York. Patrick was born in Ireland, to Bernard Ryan and Catherine McDonald.
Nicole was adopted by singer Lionel Richie. Her biological father, Peter Michael Escovedo, was a band member of Lionel Richie’s band, and is a percussionist and musical director. Escovedo is of Mexican (including Spanish and Indigenous) and Louisiana Creole (including French, African, and distant English, ancestry) descent.
Nicole’s biological mother, Karen Moss, is said to have been a backstage assistant of the band.
Of interest, StyleCaster shares 45 Celebrities You Never Knew Were Related.