Quick question but i have noticed a recurring theme in incest games here is always the mother takes custody of the daughter and the father takes custody of the son. Is this something that happens in real life? I don't have any knowledge with divorce.
Split custody is technically a real thing, but it's extremely rare for siblings to grow up not knowing/interacting with each other. If there is any kind of legally approved custody agreement (a requirement for divorce) then judges/courts very rarely like to actually permanently separate siblings. So yeah you will almost never ever see split custody with one kid granted to each parent with zero contact with the other parent/siblings that primarily live with the other parent. At a minimum there will be visitations and requirements for the kids to spend a certain amount of time with their sibling. A lot of times depending on distance it would be something like trading summers.
About the only exceptions would be stuff like if one of the siblings was in some way determined to be dangerous/detrimental to be around their brother/sister, or if the kids are all old enough (teenagers) that a judge accepts their decision that they want nothing to do with the other parent/sibling, or if multiple kids have special needs that required them to be raised in a specific separate place.
Now of course you theoretically can have a couple get an judge approved custody agreement, and then both privately agree to split custody and just not follow through on visitation rights and such and as long as no one complains and the agreement wasn't court ordered then it may never be discovered?