Mosaic panel depicting the madness of Heracles about the kill Megara and their children, from the Villa Torre de Palma near Monforte, 3rd-4th century AD, National Archaeology Museum of Lisbon, Portugal [2560×1830]

One of most shocking events in greek mythology. Although, the fact that Megara and her sons had their heroic cult in Thebes means that Greeks believed they went to Elysian fields and were happy again (being a daughter in law and grandchild of Zeus was kinda a big deal). Some ancient Greeks, judging by epitaphs we have, also believed that dead children grow up in the afterlife and marry a deity as a compensation.