Lynn Ruane (Independent) | Oireachtas source

This might seem like a strange question. I look at this and see "half-brother" and "half-sister". Are those official terms used for family? Where are they laid out? Where does that come from? Is that something that has been used as a description but is not actually a legal term to describe a family? Is it something that we have applied to siblings ourselves? What do we recognise half-siblings as? My two daughters have the same mother but would not consider themselves half-sisters, but sisters. Is it different if they grow up in the same household or are children of the same father? I am sorry to confuse the issue. I wonder what it applies to. My daughter would have other siblings belonging to her father. If there were half-siblings belonging to the father who never had a relationship with each other and never grew up in the same household, they would say they were half-brothers and half-sisters because their father happened to have a load of kids in various different parents of Dublin and they are technically seen as half-siblings. Is there a definition of half-brother and half-sister?