Hi Stanisław,
Thank you for looking through the 1832 birth record. I noted that, too, that the 1832 Piotr was komornik (as he is in all previous birth records), but in the 1835 record he was something else (now I see wyrobnik). Not impossible for him to change employment, maybe as he got older, but it is suggestive.
Then it seems he grows younger by about 5-7 years between 1832 and 1835. Hmmm. And yet, there are no other Piotr Kosins I have encountered in this area, though there are a few other Kosins (Ignacy, Jan, Stanisław, possible brothers or cousins, I cannot know until I am sure of Piotr's parents).
Piotr's son, Franciszek, at some point moves to Bieżuń, where he has my 3x great grandfather, Teodor in about 1839. Since I have not found any death record for Piotr Kosin in Kocewo up to 1862, it is possible he moved with Franciszek to Bieżuń.
Unfortunately, there are no online records for Bieżuń between 1825 and 1856, just when I would need them to confirm.
Thank you so much! You have always been so helpful to me; it helps me, too, to think things through as I write to you. I appreciate your time in reading all of this. You are very kind!