Linda Carman's three sisters - Valerie Santilli, Elaine Chakalos, and Charlene Gallagher - argue in their suit that "the facts uncovered to date warrant a finding that Nathan killed his grandfather".
Nathan Carmen's mother Linda, from Middletown Connecticut, is presumed dead.
Attorneys for Nathan Carman are asking a New Hampshire probate judge to throw out a petition filed by his aunt's seeking to have him declared the murderer of his grandfather, arguing that the dead man wasn't a legal resident of the state. Police have acknowledged that Carman is a suspect in that case, but no one has been charged.
Linda Carman was never found. Nathan Carman is now the sole owner of that account because his mother gifted to him her half before she disappeared, according to the new court filing.
In response, Nathan Carman's attorneys again wrote: "Denies".
Their lawsuit filed in July says Carman argued with his grandfather about money prior to his death, and that Carman purchased a semi-automatic rifle of the same caliber used to shoot his grandfather.
Nathan Carman, a Vermont man who was a suspect in his grandfather's killing and whose mother disappeared at sea under odd circumstances, denies having a role in either of their deaths, according to court documents filed today.
The family on Wednesday insisted in a statement that Chakalos was a "long time resident of Chesterfield, New Hampshire, and a well-known, active member of the community". "He loved the home that he and his wife Rita had built and which they shared with the surrounding community every Christmas".
In the sisters' lawsuit, lawyers for the family said that no has seen Linda Carman since she boarded the boat, the Chicken Pox, with Nathan Carman. Carman admitted he did work on the boat but denied that he caused it to sink. It also raises questions about whether the boat sank in the spot where Nathan Carman claims, alleging that the life raft "could not have drifted from Block Canyon to the position where Nathan was rescued".
The lawsuit claims Nathan put on a life vest, got in the life boat with a bag of provisions and left his mom behind.
In the response, he admits he moved the tabs but denies the rest.