While we know who one of their children is – Mary King, we cannot find a birth or baptism record for Mary. We do not know (yet) if they had other children, when they were married or where or when they were born.
Because John was a labourer in Ireland, it is possible that there are no records to be found and the trail will stop here. I am hoping not. With DNA and other resources becoming more available, hopefully something more will be found.
For now, we have very short histories.