| Though this isn't the most reliable source, Draco Malfoy states on page 223 of the U.S. hardcover of CoS that his father told him, "last time the Chamber of Secrets was opened, a Mudblood died." That would be referring to Myrtle, and I think it's safe to assume she was indeed a Muggleborn.
As stated above (Yami_Mirai), Dean's father was a wizard killed by Death Eaters (see JKR's official website). Penelope's and Lavender's blood statuses weren't discussed. I'm inclined to believe that Penelope was petrified merely because she was in the wrong place at the wrong time (and perhaps that wrong place was in the corridors with Hermione Granger- obviously Muggleborn). |
Cast of Harry Potter 
Harry Potter Chapter Titles 
Harry Potter: Patronuses
