Nils Petter Eriksson Karhula (Raudus)

I am trying to find any information on him other than the names of his children. The records I found said his birth year was <1805>, but he had a child in 1818 so I don't think the birth year is right. Nils Petter married Margareta Johansdr Kariniemi and her birth year states 1794. I am thinking this is my great grandmother Kaisa Karhula's grandparents. I could be wrong but they had a child named Petter Karhula in 1929 and I think this is Britha Kaisa's father. I would like to find out as much as I can and see how far I can go back on the Karhula side of the family. Thank you for any help you can give me. Julie Pirkola Harris