Lahamu was the first-born daughter of Tiamat

Tiamat

In Babylonian mythology, Tiamat is a chaos monster, a primordial goddess of the ocean, mating with Abzû to produce younger gods. It is suggested that there are two parts to the Tiamat mythos, the first in which Tiamat is 'creatrix', through a "Sacred marriage" between salt and fresh water,...

 and Apsu in Akkadian mythology. With her brother Lahmu

Lahmu

' is a deity from Akkadian mythology.- Mythology :Lahmu, "Hairy" is the name of a protective and beneficent deity is a first-born son of Apsu and Tiamat. He and his sister are the parents of Anshar and Kishar, the sky father and earth mother, who birthed the gods of the Mesopotamian Pantheon...

 she is the mother of Anshar

Anshar

In Akkadian mythology, Anshar , which means "sky pivot" or "sky axle", is a sky god. He is the husband of his sister Kishar. They might both represent heaven and earth . Both are the second generation of gods; their parents being the serpents Lahmu and Lahamu and grandparents Tiamat and Apsu. In...

 and Kishar

Kishar

In the Akkadian epic Enuma Elish, Kishar is the daughter of Lahmu and Lahamu, the first children of Tiamat and Apsu. She is the female principle, sister and wife of Anshar, the male principle, and the mother of Anu...

, who were in turn parents of the first gods. Lahamu is sometimes seen as a serpent, and sometimes as a woman with a red sash and six curls on her head. It is suggested that the pair were represented by the silt of the sea-bed. There also parallels between the Sumerian Creation story and the Biblical Creation story in where Adam and Eve were the first-born of the gods.

She and her brother/husband are never mentioned separately.