A local paper reported on Friday that a court ruled that the victim had shamed her family.
The Jordan Times said the man stabbed his 21-year-old sister at least 15 times in August 2003.
"The defendant lost his temper after seeing his pregnant sister and could not think rationally because of the unlawful act the victim had committed, which brought shame and disgrace to her family," the court ruled.
The unmarried victim went missing in September 2002 and later contacted her sister telling her she was pregnant. Her brother tracked her down and stabbed her, the paper said.
The court first charged him with murder, but changed that to a misdemeanour because of the damage it said she had done to the family's reputation and because it ruled the 26-year-old did not plot the killing. The family dropped charges against him.
Last September Jordan's parliament rejected an amendment to stiffen usually lenient sentences for people convicted of so-called "honour killings".
In a separate court case, a man was jailed for a year for killing his 17-year-old sister for allegedly having an affair.
The sister went missing in May 2003. She was arrested and returned to her family upon guarantees they would not harm her.
But during an argument with her brother, he pulled a gun and shot her twice, the court quoted the mother and the defendant as saying. That family also dropped charges.
Both verdicts are subject to appeals.