In the fifth episode of the Pokémon anime "Showdown at Pewter City", Flint (Brock's Dad in disguise) says the following about Brock's family situation.
His good-for-nothing father left the family to become a Pokémon Trainer and they never heard from him again. Brock's heartbroken mother tried her best to hold things together, but sadly, she passed away.
However in the Pokémon Chronicles episode "A Family That Battles Together Stays Together!", Brock returns to Pewter City and sees his mother, who is now running the gym.
Who is this woman? Was this an unexplained retcon to be his original mother? Or is this mother his stepmom?