Beach Boys Singer Brian Wilson Has Dementia, Family Seeks Conservatorship

Brian Wilson's family has filed for a conservatorship after the death of his wife, Melinda -- and they say it's because his cognitive ability has seriously regressed ... TMZ has confirmed.

According to legal docs ... the legendary Beach Boys frontman is suffering from a "major neurocognitive disorder" and taking medication for dementia -- so says his family. The docs say Wilson can't properly care for his basic personal needs such as food, clothing or shelter.

The Wilson family confirmed the news of the court filing to People, telling the outlet the family came together after Melinda's death and -- in consultation with Wilson's kids, longtime staff members and doctors -- decided to appoint two family representatives as his conservators.

The family went on to add that the decision was made to try and minimize changes to Brian's life and the lives of his children who still live at home.

Despite the conservatorship filing, the family says Wilson can still spend time with loved ones and even work on projects if he so chooses.

As we reported ... Melinda Kae Ledbetter Wilson passed away at the end of last month at the couple's home surrounded by her family.

Brian wrote on Instagram, "Melinda was more than my wife. She was my savior. She gave me the emotional security I needed to have a career."

A court hearing is scheduled for the end of April ... though it's not clear whether Wilson will attend in person.