From my own genealogy experience, evidence of kinship within Irish families can be found by looking at who the witnesses were at Catholic baptisms and marriages. My ancestors in Liverpool were clearly using a wide family network when choosing their witnesses. Given that there are gaps in the records in Ireland, this was highly useful for understanding relationships within the wider family and providing further evidence for supporting hypotheses gathered from other records. But you can't search for your ancestors by sponsor name. So I don't know who my ancestors witnessed in their local communities and thus may be missing out on identifying these relationships which would add depth to my research.
What is the purpose of this project?
Catholic Witness Index (CWI)