Michael Keaton-->Jackie Brown-->Samuel L. Jackson-->The Negotiator-->Kevin Spacey-->Glengarry Glen Ross-->Alec Baldwin-->Pearl Harbor-->Josh Hartnett
Okay, da man, I got it, finally. Blythe Danner played Martha Wayles Skelton Jefferson, the wife of Thomas Jefferson (Ken Howard) in the musical "1776" (1972), and her Oscar-winning daughter, Gwyneth Paltrow, played Patsy Jefferson, daughter of Thomas Jefferson (Nick Nolte) in "Jefferson in Paris" (1995).
And I totally used the IMDb (for the second one, not the first). Once you said it was a musical, "1776" was my first guess, and when I saw Danner's name in the credits as Mrs. Jefferson (late 18th-early-19th-century historical figure), that pretty much locked it in.
Good game, but I prefer the slightly easier one already on this thread.
Next: Bob Hope and Estelle Getty