Bruce Forsyth is among celebrities tracing their family trees on the new series of BBC One ancestry show Who Do You Think You Are?
Producers say the Strictly Come Dancing host finds a letter suggesting his great-grandfather, a leading landscape gardener, was a bigamist.
The nine-part series will also feature actor Rupert Everett, gardener Monty Don and singer Jason Donovan.
One part will feature married couple Rupert Penry-Jones and Dervla Kirwan.
Forsyth's great-grandfather, Joseph Forsyth Johnson, designed a number of UK estates and curated the Royal Botanic Gardens in Belfast.
He also created gardens in the US and refurbished Prospect Park in Brooklyn.
Forsyth, 82 - real name Bruce Joseph Forsyth Johnson - comes from a line of horticulturists including William Forsyth, who gave his name to the shrub forsythia.
The BBC said that following the recent death of his father, Rupert Everett uncovers the truth behind a family mystery and meets a relative for the first time "in the most unexpected place".
Kirwan, meanwhile, explores the life of her great great uncle, Irish revolutionary Michael Collins.
Other celebrities appearing on the series, which starts at the end of July, include Broadway star Alan Cumming and comedy actor Alexander Armstrong.