declare function local:split($x as node()) as node() {
 let $name := $x/name/text() return
 let $sons := 
  for $p in $x/children/person[@gender="M"] return local:split($p) return
 let $daughters := 
  for $p in $x/children/person[@gender="F"] return local:split($p) return
 if ($x/@gender = "M") then 
   <man name="{$name}">
     <sons>{$sons}</sons>
     <daughters>{$daughters}</daughters>
   </man>
 else
   <woman name="{$name}">
     <sons>{$sons}</sons>
     <daughters>{$daughters}</daughters>
   </woman>
}
;

<doc>{for $p in ./doc/person return local:split($p)}</doc>