K'Ehleyr had been romantically involved with Worf in 2359, but the relationship remained unresolved until 2365 when K'Ehleyr was assigned to the Enterprise-D to deal with the T'Ong crisis. K'Ehleyr and Worf nearly took the Klingon marriage oath at the time, when, unbeknownst to Worf, their liaison resulted in the conception of a child, Alexander Rozhenko.

K'Ehleyr served as a Federation ambassador to the K'mpec government, and helped orchestrate K'mpec's scheme to appoint an outsider as his Arbiter of Succession. Worf remained unaware that he was a father until K'Ehleyr returned to the Enterprise-D in 2367. She was at the time accompanying K'mpec for the meeting in which he asked Jean-Luc Picard, an outsider, to serve as his Arbiter of Succession. K'Ehleyr was murdered by Duras during the rite of succession after K'Ehleyr began to uncover evidence of Duras' wrongdoings. Worf subsequently claimed the right of vengence under Klingon law and killed Duras. Worf also accepted custody of his son, Alexander, who remained with him aboard the Enterprise-D. ("Emissary", "Reunion")

from the Star Trek Encyclopedia