Family #32a in the 1767 Grimm census.
Family #20 in the 1775 Grimm census.
Family #57 in the 1798 Grimm census.
Family #138 in the 1834 Grimm census.
Christian Pikus was born about 1748 in Pommern, in what is now Germany. His father was Georg Pikus; his mother not named. According to the 1767 Grimm census, Christian was an orphan who lived with the Christian Hendel family. That same record also gives his father's name. It is likely that both parents were alive when they began their immigration journey to Russia, and that both perished either enroute to Grimm or shortly after their arrival.
Head of the Household Christian Pikus, age 19, Lutheran from Pommern, orphan
Father Georg Pikus
Notes Lives with Christian Hendel family, #32
By 1775, Christian Pikus had married the widow Margaretha Fritz (probably Fritzler) who had four children. The youngest was only 3 years old, so Christian and Margaretha did not marry until 1772 at the earliest and possible as late as 1774 or early 1775. At the time of the census, they had no children of their own.
Wife Anna Margaretha Thiel Pikus, age 64, widow of Johannes Fritz
Step-Child #1 Katharina Fritz Rudolph, age 29
Husband of Step-Child 31 Heinrich Rudolph, age 27
Grandchild #1 Andreas Rudolph, age 5
Grandchild #2 Konrad Rudolph, age 2
Grandchild #3 Johann Heinrich Rudolph, age 1
Step-Child #2 Anna Margaretha Fritz, age 26
In the 1834 census, it says he died in 1850, so obviously that's some kind of a typo. Looking at the number keypad next to the letters on my keyboard, the 2 and 3 are directly below the 5. It would be easy for someone inputting the translated data to simply hit the wrong key and not catch the error. I am entering "before 1834 as his death year for now.
Additionally, the absence of both Christian Pikus' wife, Anna Margaretha Thiel, and his daughter Katharina, wife of Heinrich Rudolph, suggests that both women had passed away.
Head of the Household Christian Pikus, age 65 in 1816, deceased 1850 [sic]
Husband of Step-Child #1 Heinrich Rudolph, age 64
Grandchild #1 Andreas Rudolph, age 41
Grandchild #2 Heinrich Rudolph, age 18 in 1816, deceased 1830
Grandchild #3 Konrad Rudolph, age 31
Grandchild #4 Jakob Rudolph, age 25
I also could find no Pikus surnames on FamilySearch.org's website. It is very likely that the original surname was misspelled in Russian records. Some possibilities include:
Pleve, Igor. Einwanderung in das Wolgagebiet 1764-1767, Band 2, Herausgegeben von Alfred Eisfeld under Mitarbeit von Sabine Eichwald, Published by the Nordost-Instsitut - 38085 Göttingen, 2005; page 77, family #32a.
↑The 1775 and 1798 Census of the German Colony on the Volga, Lesnoy Karamysh, also known as Grimm; Published by the American Historical Society of Germans from Russia, Lincoln, NE, USA; Published 1995; family #20 in the 1775 census.
↑The 1775 and 1798 Census of the German Colony on the Volga, Lesnoy Karamysh, also known as Grimm; Published by the American Historical Society of Germans from Russia, Lincoln, NE, USA; Published 1995; family #57 in the 1798 census.
↑1834 Census of Grimm in the District of Saratov, Russia, dated 2 February 1835; Translated by Brent Mai, Concordia University, Portland, Oregon; Published by Dynasty Publishing, Beaverton, OR, USA; Published 2011; page 43, family #138.
The American Historical Society of Germans from Russia, online resources, German Origins, Pf, see: https://bit.ly/2R9zCU2.