Question: Ur-Nungal of Uruk was the sixth Sumerian ruler in the First Dynasty of Uruk, he was the father of which person that became the seventh Sumerian ruler in the First Dynasty of Uruk?

Context paragraphs:
En-nun-tarah-ana: En-nun-tarah-ana of Uruk was the ninth Sumerian ruler in the First Dynasty of Uruk (ca. 26th century BC), according to the Sumerian King List, reigning for 8 years.

Mesannepada: Mesannepada (or Mesh-Ane-pada, "youngling chosen by An") was the first king listed for the first dynasty of Ur (ca.  the 25th century BC) on the Sumerian king list.  He is listed to have ruled for 80 years, having overthrown Lugal-kitun of Uruk.

Kalibum: Kalibum of Kish was the seventh Sumerian king in the First Dynasty of Kish (after ca. 2900 BC), according to the Sumerian king list.

Ur-Nungal: Ur-Nungal of Uruk was the sixth Sumerian ruler in the First Dynasty of Uruk (ca. 26th century BC), and son of Gilgamesh according to the Sumerian king list.  He was the father of Udul-kalama.

Dumuzid, the Fisherman: Dumuzid, called "the Fisherman" (cuneiform:𒌉𒍣𒋗𒄩 ; <a href="Sumerian%20language">Sumerian</a>: "Dumuzid šukud)" originally from <a href="Kuara%20%28Sumer%29">Kuara</a> in <a href="Sumer">Sumer</a>, was the 3rd king in the 1st Dynasty of <a href="Uruk">Uruk, and <a href="Gilgamesh">Gilgamesh</a>'s predecessor, according to the <a href="Sumerian%20king%20list">Sumerian king list.  The king list also states that he singlehandedly captured Enmebaragesi, ruler of Kish, and it claims he ruled in Uruk for 100 years — far fewer than the 1200 years it ascribes his predecessor, Lugalbanda "the Shepherd".  His given name means "faithful child" in Sumerian.

Ishbi-Erra: Ishbi-Erra (Akkadian: "Išbi-erra", name was written phonetically in cuneiform: "diš-bi-èr-ra", in contemporary inscriptions; "fl. " "c." 1953 BC — "c." 1921 BC by the short chronology of the ancient near east) was the founder of the First Dynasty of Isin.  Išbi-erra of the First Dynasty of Isin was preceded by Ibbi-Sin of the Third Dynasty of Ur in ancient Lower Mesopotamia, and then succeeded by Šu-ilišu.  According to the Weld-Blundell Prism, Išbi-erra reigned for 33 years and this is corroborated by the number of his extant year-names.  While in many ways this dynasty emulated that of the preceding one, its language was Akkadian as the Sumerian language had become moribund in the latter stages of the Third Dynasty of Ur.

Puannum: Puannum of Kish was the sixth Sumerian king in the First Dynasty of Kish (after c. 2900 BC), according to the Sumerian king list.

Mesh-ki-ang-gasher: Mesh-ki-ang-gasher ("Mèš-ki-áĝ-ga-še-er ", "Meš-ki-aĝ-gašer "; also transliterated "Mes-Kiag-Gasher", "Mesh-Ki-Ang-Gasher", "Meskiagkasher", "Meckiagkacer" and variants) was a Sumerian ruler and the founder of the First Dynasty of Uruk and the father of Enmerkar, according to the Sumerian king list.  If a historical ruler, he would have flourished in ca.  the 28th century BC (Early Bronze Age II).

Udul-kalama: Udul-kalama of Uruk was the seventh Sumerian ruler in the First Dynasty of Uruk (ca. 26th century BC), according to the Sumerian king list.  He was a son of Ur-Nungal and grandson of Gilgamesh.  However, unlike his predecessors, he left no other known documents or relics mentioning his name, and he may have been one of several minor kings of Uruk added to the list, who reigned when hegemony was actually held by the first dynasty of Ur.

La-ba'shum: La-ba'shum of Uruk was the eighth Sumerian ruler in the First Dynasty of Uruk (ca. 26th century BC), according to the Sumerian king list.

Supporting paragraphs: Ur-Nungal Udul-kalama
Answer: Udul-kalama of Uruk