One way I try to find if a couple are parents or not, is by trying to find the probate records for the ones I suspect, as if there is one, the person I'm looking for parents for, should be mentioned. :)
If they live in the same village / farm as the birth place of your ancestor, it is probable but not certain they are the right people. Then follow them, and look for siblings of your ancestor in the birth records around the birth of your ancestor to learn about the rest of the family.
Edit: to say that when the patronymic differs from Olsdotter to Andersdotter, it is most often the wrong couple, but could still be Lars who re-married another Brita.
Also, check the births of Olof and Lars who are still living in the household of Lars Larsson.