Relatives of and are seeking damages of $10 million, according to the lawsuits in Fairfax County Circuit Court.
They were the only families who did not agree to an $11 million settlement with the state last June. Student Seung-Hui Cho killed 32 people before fatally shooting himself on April 16, 2007. The gunman's estate also is named as a defendant in the lawsuit filed the last day before the statute of limitations had expired.
The lawsuits claim Virginia Tech failed to protect its students and is directly liable for gross negligence. They further claim the university is liable for a few of its officers and employees "who were deliberately indifferent to the safety needs of its students."
Virginia Tech owed Pryde and Peterson "a reasonably safe campus" and breached its duties, which the lawsuits call a "proximate cause of" their deaths. The lawsuits further accuse Virginia Tech of trying to cover up the start of the killing spree at a dormitory that morning rather than warning students that an armed man was on campus.
Some families have lingering animosity toward administrators and feel they've never received an adequate explanation of officials' actions that day. President Charles Steger convened a meeting with top administrators after Cho killed two students in the dorm, but more than two hours passed before an e-mail informed the campus.
By then, Cho was chaining the doors of Norris Hall shut in preparation for a bloodbath that had students cowering under desks and jumping from windows. Officials still don't know why Cho, a loner who had attracted little attention, killed so many people.
The lawsuits also claim a local health center where Cho had gone to say he felt suicidal did not adequately treat or monitor him.
Neither family immediately responded to messages Thursday.
Virginia Tech spokesman Larry Hincker, who is named as a defendant along with Steger, would only confirm the lawsuits had been filed.
Pryde, 23, of Middleton, N.J., was a graduate student in biological systems engineering seeking her masters degree.
Peterson, 18, of Chantilly, Va., was a freshman majoring in international studies.