Rudolph Fromgermany OR Sweden

I am looking for the parents of my g grandmother, she was supposedly born 16 feb 1850 gottenborg Sweden. the names I have for are carl johan Petersen father and charlotte Rudolph mother. I cannot find any record of her birth and to confuse things further her father is named frantz Petersen on her marriage certificates in Norway. 1st marriage 1868 ti greger samsing in asargstrand Norway 2nd marriage to andreas friedrich krohn oslo jan.1878. any help will be appreciated cheers anne