Complex sentence: Chatty Cathy's voice unit was designed by Jack Ryan, Mattel's head of research and development; he had also been responsible for designing the Barbie doll after a German doll called Bild Lilli in 1959.
Split into simpler sentences: Chatty Cathy's voice unit was designed by Jack Ryan. Ryan had also been responsible for designing the Barbie doll after a German doll called Bild Lilli in 1959.