My first issue that I uncovered was the use of "do" or "de" which I figured was like I found with the French-Quebec surnames I was researching used as a title for "from" or "of" so it could be the son/daughter of, or from a certain village/town.
I know Wikipedia is not the most reliable place for information but that was pretty much what was stated on the site:
Prepositions that can be used in Portuguese surnames are da, das, do, dos and de, such as in Luís de Sousa, Maria da Conceição, Osvaldo dos Santos, Luísa das Neves, etc. and mean "from" or "of". Da, dos,
Back to the surnames it also looks like they were forced to use, and further reading suggests that there was no one way to use the surname. So the wife might keep her surname and the add her husbands, and the children's names could have the surname of the mother first then father's or even switched around.
I am not sure how this will work in doing my research but at the moment I am pretty lost. This started when I was given what I thought was the middle name of the person with a surname. That surname was wrong so the added the De surname. I was still thinking that middle name was the middle name but that was verified that it was his last name.
If anyone has done any research in Portugal or Brazil I could really use the help to try and figure some of this stuff out.
I have some of the surnames for the families I am researching but at this time I will not post them. If anyone can help I can send them an email with the surnames to see what is possible.