"This is about a pitiless egoist. He viewed his family as his property," Judge Winfried Hetger said.
According to ABC News, the defendant, a 48-year-old unemployed truck driver identified only as Detlef S., sat emotionless as he was convicted of 162 counts of sexual abuse.
Detlef, a former resident of Fluterschen, was accused of abusing his stepson and stepdaughter starting in 1987, when they were 4 and 6 years old, and continuing until 2010.
According to Hetger, Detlef also abused his biological daughter, who is now 18.
"When she was 12 years old he took her into a forest and raped her inside his Toyota Corolla," the judge said. "He explained to her that this was something really great."
Detlef forced both the biological daughter and the stepdaughter into prostitution, the judge said. In August, the biological daughter went to police with the molestation and rape allegations that resulted in her father's arrest.
Judge Hetger also ruled that Detlef should remain imprisoned indefinitely because there is a high risk that he could offend again if released.
Speaking with ABC News, Detlef's stepson and his sister, identified as Bjoern B. and Natascha S., said they were shaken by the verdict but happy that justice was served.
"Today is a day of truth, a day of justice," said Bjoern B., now 28. "Now we will see how we can continue our lives."