Brian’s mental problems began in the ‘60s, but I don’t believe that he was under conservatorship until circa 1991 when his cousin Stan Love (father of the NBA’s Kevin Love) sought to become his conservator. That was during the period when Brian was being controlled and overmedicated by his crackpot psychologist Gene Landy. Brian didn’t want Love as his conservator but he agreed to a neutral 3rd party. When Brian got remarried, I think his wife became his conservator and eventually they got out from under the court system. But, yes, there absolutely was a period c. 1991-97 when Brian was under conservatorship but still performing, recording music, etc.
Weren’t his brothers feeding him cocaine and hamburgers in bed in the 70s to write songs for them?