George McFly = Dead
Lorraine: Marty! George, your father is in the same place he's been for the past 12 years. [takes a sip] Oak Park Cemetery.
Biff explicitly states that he killed him, presumably in order to get to Lorraine.
The rest of the family = Not doing so good
Biff: Oh, wouldn't I? First your daughter Linda, I'll cancel all her credit cards. She can settle her debts with the bank all by herself. (He walks up the stairs.) Your idiot son, Dave, I'll get his parole revoked. And as for Marty, well, maybe you'd like all three of your kids behind bars just like your brother Joey. One big happy jailbird family.
Marty = In boarding school
Biff: Did you get kicked out of another boarding school? (Lorraine takes another sip of her drink.) Damn it Lorraine, do you know how much perfectly good dough I've spent on this no good kid of yours,
All quotes from the BTTF2 script
Jennifer = Unknown
Her family still live in the same house, albeit with bars on the windows.
They drove the rest of the way to Jennifer's house.
Even in the dark, Marty could see THE PARKERS in big block Ietters on
Marty and Doc managed to get Jennifer out of the car, and gently
carried her toward the house. Doc nodded ahead to the front porch. - BTTF Part 2, A Novel
Presumably she's alive in this timestream or else she would have started to fade but that's about all we know.
Doc Brown = In an insane asylum
The paper was dated July 1983. The headline at the top of the page read:
EMMETT BROWN COMMITTED. Crackpot Inventor Declared Legally Insane!
Einstein = Unknown
Again, since he didn't fade we can assume that he's still alive in this future