Paul Branstetter, one of the couple's three living sons, said he had no comment about the lawsuit.
The lawsuit filed against the Branstetters' estate is pending.
In March, a district judge ruled the couple were not considered employees of OSU and are not protected by Oklahoma's Governmental Tort Claims Act.
Lawyers representing the Branstetters have claimed the couple were “employed” by the university because they frequently volunteered their time and energy to help university employees conduct school business.
“The Branstetters were carrying out the business of Oklahoma State University as unpaid volunteers by transporting Mr. Serna and Mr. Budke,” one of the Branstetter family attorneys wrote in a motion to dismiss the lawsuit.
“It is for these reasons ... the Branstetters are considered persons that fall within the statutory definition of ‘employee' of the (Governmental Tort Claims Act), and (are) entitled to dismissal.”
What's at stake?
While the lawsuits filed against the Branstetters' estate do not specify how much Shelly Budke and Serna's parents are seeking, the Branstetters appeared to be wealthier than most Oklahomans.
Records available to the public do not say how much money Olin and Paula Branstetter had when they died, but do reveal that Olin Branstetter owned numerous oil and gas properties, real estate and that he had funded the education of his grandchildren using “cash and securities” before his death.
Olin Branstetters' last will and testament also discloses that he had established a trust fund to benefit his wife and three sons following his death and that he owned stock in Sonic Corp. and Bank of America in the years leading up to his death.
The lengthy document lists numerous charities, relatives, friends and others as beneficiaries.