Complex sentence: In 1993, he became a member of the short-lived Johnny's unit J-Eleven and also a member of KinKi Jr., a back-up group for KinKi Kids.
Split into simpler sentences: In 1993, he became a member of short-lived unit called J-Eleven. That same year he was also in KinKi Jr, a back-up group for KinKi Kids.