digraph G {
  "Joseph" -> "Claire"
  "Paul" -> "Marie"
  "Luc" -> "Marie"
    "Luc" -> "Claire"
    "Bernard" -> "Marie"
    "Bernard" -> "Claire"
    "Bernard" -> "Jeanne"
    "Francois" -> "Suzanne"
    "Francois" -> "Anne"
    "Francois" -> "Jeanne"
}