One of my female ancestors was described as a "hija de padres no conocidos" in her marriage record (partida matrimonial), but in her marriage information (información matrimonial) she was described as a "hija natural (según dicen) de..."; both daughter and mother bore the same surname. I do believe that some children of "padres no conocidos" were, in fact, natural children who deliberately concealed the identities of their parents.

V.Q.C.

i don't really know. i wonder if in some case of hijo(o/a) adoptiv(o/a) the child didn't know who their actual parents were(i think that's the case for some who are labeled as padres no conocido also, but padres no conocidos can also refer to 'natural' children.)

also last names weren't always passed down in a consistant manner. for example, on person on my tree didn't get either parent's last name, and instead got his last name derived from the place he grew up at.

Based on what I've seen on numerous records I can assume that adoption wasn't based on any set of rules per say,(although they exist) and thus the situations behind each case would vary. Closer relatives would be more likely to take kids as their own, now taking a kid didn't mean they were always considered adopted, I think the adoption was "official" when there was some inheritance at stake, but definitely not a rule either.

Taking on a specific surname is not uncommon, even by biological sons/daughters specially among big Spanish families we see often kids making their own "set" of last names, now in your ancestor's case it seems like he could be in fact his adoptive mother relative and thus he used her last name but again, this is not a rule and could easily be that he just was too close to her.

Official adoption is usually not seen too often, but once we read many records we can see that there were many families that "house in" relatives at the point they were considered part of them, and in many cases the true identity behind them is unknown, I wouldn't consider adoption unusual but poorly recorded.

As for records, well they were not really systematic, many information was "loosely" recorded and many things important for us now were left out, some records would barely say anything of the adoptions. Also some kids would be adopted regardless of their parents been actually dead, (like natural or illegitimate) kids, all of this would not appear on records and one have to play detective in order to find more about it. Therefore, even if the records don't mention some aspects it doesn't mean they didn't happen, and the older the manuscripts the more discrepancies we encounter unfortunately.

Hope it helps a little.

RJ Quiralta