The Most Shocking And Disturbing 'Killer Siblings' Of All Time

Siblings are often close — they'll do anything for each other. But does that include murder?

Sometimes, the answer is yes, as shown on Oxygen series "Killer Siblings," which returns for Season 3 on Friday, December 3 at 8/7c. The series tells the twisted stories of some of the most maniacal siblings in history through exclusive interviews and firsthand accounts, revealing the disturbing murders these killers committed together.

Before the new season premieres, look back at some of the most disturbing cases featured in past seasons of "Killer Siblings."

1. Lyle and Erik Menendez

Lyle and Erik Menendez in court. Photo: Getty Images

Maybe the most famous killer siblings ever, the Menendez brothers were behind the deaths of their multimillionaire parents, Kitty and Jose. In 1989, Lyle and Erik Menendez, who were 21 and 18, respectively, at the time, claimed they came home to their California mansion to find their parents shot to death.

However, their spending sprees after the murders, as well as inconsistent statements they made, raised eyebrows. The two eventually confessed to killing their parents, but insisted they had murdered them not over greed, but because their father, Jose, was abusive. Their self-defense argument didn't work, and they were both sentenced to life in prison in 1996.

2. Matthew and Tyler Williams

Benjamin Matthew Williams, left, and his brother, James Tyler Williams, listen to the proceedings during their arraignment on murder charges of two gay men in a Shasta County Courtroom, in Redding, Calif., Thursday, July 29, 1999. Photo: Rich Pedroncelli/AP

While Matthew Williams, 31, and his brother Tyler, 29, were raised in a fundamentalist home in California, those around them didn't realize how extreme their beliefs had become. After leaving the Navy, Matthew became deeply involved with a church called the Living Faith Fellowship, according to Salon. He became obsessed with “purification,” according to his former friend Jeff Monroe. 

That obsession turned deadly in July 1999, when Matthew, with the help of brother and willing acolyte Tyler, murdered a gay couple, Gary Matson and Winfield Mowder, in their own home. Matthew and Tyler knew the couple as they owned a local farmer's market. The murders were eventually connected to the brothers, and when their home was searched, police uncovered literature from white supremacist group World Church of the Creator and evidence they had set fire to nearby synagogues. Tyler was sentenced to 50 years for his role in the crimes, while Matthew died by suicide in prison in 2002, according to the New York Times. 

3. Pete and Pat Bondurant

Pete and Pat Bondurant made a particularly imposing pair in their small Tennessee town: The twin brothers weighed about 300 pounds each, with violent tempers to match their size. They were known to be drug dealers, and plenty of people looking for drugs hung out at their farmhouse, which was the center of their operation.

Three people wouldn't leave that farmhouse alive. Gwen Duggar, 24 was killed after visiting in May 1986. Pat's estranged wife later told police Duggar was killed by Pat and Pete after they gave her pills and Pat sexually assaulted her, according to "Killer Siblings."A local man named Ronnie Gaines was murdered by Pat after Pat accused him of stealing his wallet.

After they were brought in for questioning about the murders, Pat claimed his alibi was girlfriend Terry Lynn Clark. She was found dead in November 1986. The brothers insisted she had died by suicide, but no one believed him. Investigators eventually gained enough evidence to connect the pair to all three killings. Pat is now serving life in prison, while Pete served 25 years. He was released from prison in 2016.

4. The Fryer Brothers

Alan Fryer, David Fryer and James Fryer

The Gitchie Manitou murders in 1973 are so infamous, they served as inspiration for the plot of a season of "Fargo." On November 17, 1973, five teenagers from Sioux Falls, South Dakota — Stewart Baade, 18, his brother, Dana, 14, Mike Hadrath, 15, Roger Essem, 17, and Sandra Cheskey, 13 — headed to the Gitchie Manitou State Park in Iowa to hang out. Their night of low-key revelry ended when they were randomly ambushed by a trio of brothers: Allen Fryer, 29, David Fryer, 24, and James Fryer, 21.

When the men, who were out poaching deer, came across the teenagers, Allen ordered Cheskey into his truck. The other two brothers executed the teenage boys. Cheskey was raped, but let go by the men, who warned her not to tell anyone. Cheskey eventually went to the authorities, and the murderous brothers who were all sentenced to life in prison.

5. Catherine Suh and Andrew Suh

Andrew and Catherine Suh

Sisters can be just as deadly as brothers. After the Suh siblings' mother was murdered in 1987, Catherine, who was five years older than her brother, Andrew, became his legal guardian at the age of 18. The siblings were quite close — close enough that Catherine was able to convince Andrew to kill her boyfriend.

Andrew, who was a bright and promising college student, was told by Catherine that her boyfriend, Robert O’Dubaine, a local bar owner, was beating her and stealing her money. She urged her brother to step up and kill O'Dubaine, according what Andrew later told police. On Sept 25, 1993, he shot the O'Dubaine to death.

Andrew maintained the crime was carried out because of a sense of family duty — and not to get a cut of O'Dubaine's $250,000 insurance policy. Both siblings ended up behind bars. Andrew was sentenced to 100 years behind bars, and Catherine was sentenced to life without parole. Andrew now says he believes his sister murdered their mother, too, according to a 2017 interview with the Chicago Tribune.

For more disturbing and shocking stories of murderous siblings, watch "Killer Siblings," which returns for Season 3 on Friday, December 3 at 8/7c on Oxygen.