Cuckoos pose parental puzzle

Cuckoos puzzle me. Their parasitic habits seem to offer freedom from parental labours, yet over recent years I've seen three Horsfield's Bronze-Cuckoo (Chalcites basalis) pairs feeding immatures of their own species - perhaps indeed their own young. Just as baffling, how did the species first come to pop eggs into the tiny hidden domed nests of Red-backed Fairy-wrens? After the first, imprinting would explain continued laying: the cuckoos recognise fairy-wren nests are theirs. But the first ... ?

And Little Bronze-Cuckoo (Chalcites minutillus) can on a rare day be seen in what might be family groups of three or four, though the young appear more often to be begging than receiving food. 

Not seen anything similar with Brush Cuckoos (Cacomantis variolosus). Perhaps others have?
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