Heather's Adoptive Parents

Heather's parents were held hostage by Alvin the Treacherous while he blackmailed Heather to get information on training dragons.

Dragons: Riders of Berk
Heather finally confessed that her parents were captured in Heather Report Part II. However, the riders had already found out she was working with the Outcasts, so no one believed her.

When Astrid, who was disguised as Heather, was about to leave with the Book of Dragons, Alvin came back with the two, revealing the truth. He would return them to "Heather" for the book. Astrid then tries to rescue them, but is found out by Alvin, when he touched her dyed hair, and is forced to take them to Hiccup and the others.The couple was surprised to see Toothless, and were carried by Stormfly back to Berk.

Heather's parents then left Berk with their daughter back home to their island.

Race to the Edge
In Have Dragon Will Travel Part I and in Have Dragon Will Travel Part II, Heather mentions that her village was destroyed in a raid by Dagur. She also insinuates that her parents were killed in the raid. Heather also revealed that her parents were actual adoptive parents, as she told Hiccup she lost her father. She could remember her father to have big rough hands and she could always remember his smell.