Cassidy’s daughter, “Gossip Girl” actor Katie Cassidy, 38, and his son, songwriter Beau Cassidy, will be there. The ...

Cassidy’s biggest hit, “I Think I Love You,” went No. 1 on the Billboard charts and won the NARM award for fastest-selling single of 1970. By 1971, Cassidy and his step-mom and Partridge Family costar ...