2:48 PM PT -- Carrie's daughter, Billie Lourd, claims her Uncle Todd knows exactly why he was left off the guest list for Carrie's Walk of Fame ceremony. She told us it all goes back to how Todd, as well as Carrie's sisters, publicly mourned her.
Billie says she's pissed they did interviews and wrote books about Carrie after she died, and she openly admits she's the one who made the call to officially ban them from the W.O.F. festivities.
Carrie Fisher's brother says he'd be well within his rights to show up to her Hollywood Walk of Fame Ceremony and cause a fuss over getting snubbed from attending ... but he's opting to keep things "classy" in honor of his late sister.
Todd Fisher joined us Wednesday on "TMZ Live" and we asked him why he and Carrie's sisters are officially off the guest list for the big event Thursday on Hollywood Blvd.
Todd says he doesn't know what's behind the snub ... but strongly hinted it's Carrie's daughter, Billie Lourd, calling the shots. He admits they don't really have a relationship these days, but seems genuinely puzzled as to why.
There's definitely some bad blood ... Carrie's sisters, Joely Fisher, and Tricia Leigh Fisher ripped Billie on social media for the snub. Todd seemed to be trying to play nice, as he would only say he hasn't talked to his niece since she ghosted an invite almost 3 years ago to visit a dying relative.
Todd says he's the one who got the ball rolling on Carrie getting her star on the Hollywood Walk of Fame and was shocked when he found out he didn't make the 30-person guest list.
But, if the status quo doesn't change, Todd says he's prepared to sit this one out ... telling us Billie's people have made it clear to him he should back down.