I did one for maids, butlers and home health care workers from other countries, now here is one for the US. I can think of quite a few. Feel free to add your own! ;)

Florence-Marla Gibbs (Jeffersons)
Tony Micelli-Tony Danza (Who's the Boss?)
Charles-Scott Baio (Charles in Charge)
Joey-Joey Lawrence (Melissa and Joey)
Harriette Winslow-Jo Marie Payton (Perfect Strangers)
Nell-Nell Carter (Gimme a Break!)
Mrs. Garrett-Charlotte Rae (Diff'rent Strokes)
Alice-Ann B. Davis (The Brady Bunch)

Benson - Robert Guillaume (Soap, Benson)

Hazel-Shirley Booth (Hazel)

If we extend to non-sitcoms, The Big Valley also qualifies.

Mr. French, 'Family Affair'

Lurch, 'The Addams Family'

Fran, 'The Nanny'

Hop sing (bonanza)
Hey boy (have gun will travel)

Silas(The Big Valley), Esmarelda(Bewitched), Beulah(Beulah)