Tony York, the youngest son of 49ers owners Denise DeBartolo York and John York, was found dead on Friday in Sausalito.
Tony York was the younger brother of CEO Jed York.
A team source said it is believed Tony York committed suicide.
The Marin County Sheriff’s Office released a statement saying “an investigation into the cause, mode, manner and circumstances of death is currently underway.”
Jed York address the 49ers following Sunday's win over the Broncos.
“This hasn’t been the easiest year for any of us. It’s probably the understatement of the year. My brother was a great kid. He loved everything about this, he loved everything about you guys. You know, it was hard for him sometimes, and I think he’s at peace now.
“But I want you guys to know this, and I talked to Kyle and John a little about it last night: Bill Walsh said something, ‘Champions behave like champions before they’re champions.’ This team is going to be a champion. I’m going to leave a ring when we get one for my brother.”