I think that your chances of finding their parents, if that is what you are looking for, are not great, because the further back you go, the more gaps there are in the records, and you cannot assume that just because there is only one candidate does not mean that it's the right person.
Have you looked at the originals of the marriage and baptism records? If not, this is your next step, because these might contain additional information, for example where exactly they lived and the names of witnesses to baptisms, who may be family members.
Once you know where they lived you could try to see if there are any records of the estate or landowner from whom they rented their house or farm or whatever. The size of their holding might give a clue as to how poor or wealthy they were.
They might also crop up in the minutes of the Kirk Session, for example if they became paupers of elders, or if they were summoned to be dealt with for some sin, the usual one being extramarital or antenuptial fornication.
Part of Cabrach is in Banffshire and now comes under Moray, and there might be some reference to them at LIBINDX
http://libindx.moray.gov.uk/mainmenu.asp if they lived in the Banffshire part.
