"We know the investigation will eventually show they weren't negligent," Bland's younger sister, Laura Martz, 47, tells PEOPLE. "James took piloting very seriously. If he felt the plane wasn't maintained properly, he would've refused to fly that day."
"Whatever happened on the runway, I'm sure it was beyond [the pilots'] control," she adds.
The widow of Barker's assistant, Chris Baker, 29, who died in the crash, is suing Bland's estate among others. The lawsuit alleges pilots Bland, 52, and Sarah Lemmon, 31, were "poorly trained" and "negligently decided to abort and/or reject takeoff."
Barker, 32, who like DJ AM, 35, was severely burned, filed a lawsuit Nov. 21 that features similar wording, although he and the mother of his bodyguard who also died fell short of suing the pilots' estates.
Pilot Was "Meticulous""James was such a meticulous person, he was the type who wouldn't pay his bills even a day late," Martz says, adding her brother had 32 years flying experience. "He also had total confidence in the abilities of Sarah."
A family member of Lemmon declined to comment.
Peter Knudson, a spokesman for the National Transportation Safety Board, which is investigating the incident, says such investigations can take 12 to 18 months to complete.
"It's far too early to say who or what is to blame in this crash," says Knudson. "We're still in the fact-gathering stage regarding this case."
Despite the accusations, Martz says she understands why the victims are seeking legal action.
"I don't blame them for suing," Martz says. "It was to be expected; that's just the way our society functions. In fact, I'd love to be able to talk to Travis Barker and DJ AM about my brother's final moments."
Martz says she's reached out to the pair, but hasn't yet received a response.
"This was just a complete tragedy all around, and I just want to know what happened from [Barker and DJ AM's] perspective," Martz adds.
Travis & DJ AM lucky to be alive following crash