Sydney Penny played the young "Meggie" in the first part of The Thorn Birds. Penny is a popular American actress, from 1993 to 2008 she starred in the series All My Children, and from 2003 to 2005 she was part of the main cast of The Bold and the Beautiful. In 2014, she starred in several episodes of the series Pretty Little Liars.

In The Thorn Birds, Jean Simmons played "Fiona Cleary", "Meggie's" mother. Simmons has appeared in countless Hollywood films and was nominated for an Academy Award for her performance in the classic Hamlet in 1948. She won two Golden Globe Awards and an Emmy for The Thorn Birds. Simmons also starred in the series North and South for eleven episodes. She died of lung cancer on January 22, 2010 at the age of 80.

Richard Chamberlain and Rachel Ward were one of THE on-screen couples of the eighties. The two actors celebrated a little The Thorn Birds reunion in 2012, when they appeared on the PBS show Pioneers of Television. They seemed pretty happy about seeing other again!