With no legal rights at all (and none that could be conceived or enforced), step-parents are the ones who are at risk of being expelled from all connection with children they have supported - even after many years of cultivating the demanding relationship - if the set-up with the natural parent goes wrong. Like crawling across a minefield in the dark, they have to feel their way around the jealousies of the estranged parent and the wounded feelings of grandparents, while negotiating a position as both friend and authority figure for children with whom they have no natural kinship and command no automatic respect. If your own children could try the patience of a saint, somebody else’s might drive you completely crackers when you have to live with them every day. Ask any teacher - though they, at least, can retreat with a pay-packet to their own home at the end of the working day.