Family #8a in the 1767 Grimm census.
Family #92 in the 1775 Grimm census.
According to the first census of Grimm in 1767, Johann Adam Rusch and his sister Anna Barbara were orphaned, probably at some point on the journey from St. Petersburg to the Volga region. They were taken in by Johann and Angelina Braun.
1767 Grimm Census 
In the 1775 census they are still living with the Braun family, but his sister's middle name is mistakenly given as Pavlova. There is a chance that may have been their mother's last name at birth, but it doesn't sound German enough to me. I think it was a census taker error.
1775 Grimm Census 
He is not listed in the 1798 census or the 1834 census, and at this point it's impossible to know if he married and had any children before he passed away, whatever the date. There were two additional Rusch families in the 1775 census, headed by Samuel and August Rusch, but they don't appear to be related to Johann Adam and his sister. Johann Adam's father was Michael Rusch, and it's possible that he was a son of Samuel or August Rusch, but there is no evidence to support that at this time.
I believe there is an error in the 1767 Grimm census regarding the two Braun families, listed just a few families apart in the census, and the Rusch orphans. The listings look like this:
In the census listings above, it appears that the Rusch orphans were living with Andreas and Dorothea Braun and their son Johannes.
The wording is odd: Living with Andreas Braun in household with Johannes Braun in the Andreas Braun listing, not in the Johannes Braun listing. It's possible the two men were brothers, but they still had separate households in the 1767 census. Did one man take responsibility for the orphans while the children lived with the other family?
HOWEVER, in the 1775 Grimm census, the listing for the family looks like this:
In the 1775 census, there is no listing for an Andreas Braun, his wife Dorothea, or his son Johannes. Most likely Andreas Braun passed away; minimally his wife could have remarried and taken her son to live with her in her new husband's family. Or perhaps the entire family perished. But what happened to the orphans? They appear to have switched households, now (in 1775) living with Johann and Angelina Braun and their two daughters. That doesn't sound like a simple switch unless the Braun men were connected in some way, and Johannes took in the orphans after his brother's/cousin's/friend's death. The 1767 census does have that quirkly sentence, Living with Andreas Braun in household with Johannes Braun although we know the two men lived in two households, but it makes it seem like there is a stronger connection that just immigrants with the same surname.
In 1798, Johannes Braun was a 67-year-old widower. The only child who remained living with him was daughter Anna Dorothea, who by that time had married Johann Valentin Ramig and one child living with them. Anna Dorothea's age is a match with the 1767 and 1775 census records. Angelina clearly passed away prior to 1798.
This is not a huge issue for the Rusch orphans, especially if they were not blood relatives with the Brauns. But it is interesting to learn that something happened to Andreas and Dorothea Rusch, something not recorded in a census, and that the orphans who lived with them went to live with the other Braun family in Grimm.
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