I am sorry, but there is no birth entry of C. Heinrich (August) MEYERMANN in Langenholtensen.
I found 6 children of Hans and Sophie MEYERMANN between 1805 and 1822. The oldest son of them - the vet Eduard MEYERMANN - is the father of Georg Christian Hermann MEYERMANN (*1839 - "erstes eheliches Kind / 1st child in marriage").
My Presumption: Maybe they had a child before marriage and it was born somewhere else. Sometimes unmarried mothers from this villages went to the birth house (Königliches Entbindungshaus) in Goettingen, to get the child secretly. In 1828 Eduard was 20 years old and I guess he was in the university (Goettingen!?) in that time.
Viele Grüße aus Langenholtensen
P.S.: Vielen Dank für das "young man". ;-)