Lal

Lal was a Soong-type android constructed by Data in 2366 in an effort to both continue his creator, Noonien Soong's, work and to experience the act of procreation. Lal was activated genderless and was allowed to choose its own identity, settling on that of a Human female.

Lal soon began to exceed her specifications, developing emotions and becoming more Human than her father ever achieved. Unfortunately her experiences were short lived as she suffered a fatal cascade failure in her neural net. 

Lal remained in Data's thoughts for many years to come. During his experimentation with painting, he painted a portrait of Lal, which he later showed to his "mother" Juliana Tainer when she visited the USS Enterprise (NCC-1701-D) in 2370. 

After installing his emotion chip, Data found himself mourning Lal's death, an experience which caused him distress. 

In 2376 Lal was one of several prominent people and events Data recalled when he suffered flashbacks due to exposure to the Orb of Memory. 

In 2384, with the aid of the immortal known as Flint, Data was able to restore Lal's consciousness. 

Alternate versions
In an alternate reality, Data's creation of Lal was delayed by several months, due to severe weather on Galtinor Prime and the postponement of a cybernetics conference there. In this reality, Jean-Luc Picard was able to focus on Lal's then-current presence on the Enterprise during his captivity by the Borg, thus allowing their destruction (and Picard's death) at the hands of Will Riker, who then became captain of the Enterprise. Lal survived a near-fatal cascade failure with the assistance of Dr. Noonien Soong, and was taken by Admiral Anthony Haftel to the Daystrom Institute Annex on Galor IV. There, she became the template for the mass-production of androids intended to go into battle against the Borg.