I cut down these examples as they contained natter and both examples and aversions that aren't notable at all.
Possibly Hermione's parents in Harry Potter. Ron's parents are known to most at least as Molly and Arthur Weasley, and Harry's are even referred to as James and Lily Potter, but the actual names of Hermione's parents are never given. They are either referred to as "Mr. and Mrs. Granger," "Mum and Dad," and "Hermione's parents."
The parents of most of Harry's classmates remain nameless, which is weird considering how much Rowling loves Continuity Porn.
In the specific example of Hermione's parents, Hermione gave them Fake Memories prior to the seventh book. They are referred to as "Wendell and Monica Wilkins", using their fake first and last names, by Hermione.
Every parent who plays a major role, or who Harry at least meets, gets a first name. Hermione's parents are likely unnamed (as are most of his classmates) due to the Law of Conservation of Detail.
iCarly: Enforced with Spencer and Carly's parents, wherein their names are never disclosed throughout the series. Or even if their mother is alive.
Zigzagged with Freddie's mom, Mrs. Marissa Benson; likewise with Gibby's mom with the name Charlotte.
iWon't Cancel the Show finally stated that their dad's name is Steven Shay.
iSam's Mom: Sam's mom's name is finally revealed as Pam.
I cut down these examples as they contained natter and both examples and aversions that aren't notable at all.