Harry Potter, Ronald Weasley and Hermione Granger.
Although Albus Dumbledore and Lord Voldemort are also main characters in the series.
Harry Potter, Ron Weasley, and Hermione Granger are the three main characters in Half-Blood Prince.
There are more than three books in the Harry Potter series so it is not a trilogy.
Harry Potter and the Philosopher's Stone (1).Harry Potter and the Chamber of Secrets (2).Harry Potter and the Prisoner of Azkaban (3).
Harry Potter owns all three of the Hallows.
Harry Potter, Ron Weasley, and Hermione Granger. However, Albus Dumbledore and Lord Voldemort/Quirrell are also main characters.
Loads of things... Read the books.
Harry Potter isn't a trilogy, there are seven books not three. You can find a list of the deaths in the series in related questions.
More than three characters were killed, see related questions for a full list.
Harry Potter and Hermione Granger are fictional characters, they don't exist in real life. In the series, Harry had three children with Ginny Weasley: James Sirius, Albus Severus and Lily Luna Potter. Hermione had two children with Ron Weasley: Rose and Hugo Weasley.
There were more than three, see related questions for a full list.
No, Ginny survived the series. She later went on to marry Harry Potter and together they had three children named James Sirius, Albus Severus and Lily Luna Potter.
Bill and Fleur have three kids: Victoire, Dominique and Louis. All of the characters names and information on all of the Harry Potter world can be found on Harry Potter Lexicon.