I am related to two of the Grease cast!
1) Stockard "Betty Rizzo" Channing: 20 degrees and 18th cousins 2x removed
2) Jeff "Kenickie Murdoch" Conaway: 22 degrees and 21st cousins 2x removed
Other non-related Grease cast members:
20 degrees: Lorenzo Lamas; 21 degrees: Joan Blondell and Dinah Manoff; 22 degrees: John Travolta, Eunice West and Jan Hellier; 24 degrees: Olivia Newton-John; 25 degrees: Frankie Avalon