jQuery seleccione uno mismo y hermanos
$(this).siblings().addBack()
Lonely Curly Boi
$(this).siblings().addBack()// Sibling with class name
$(this).next( ".someClassNameOfSibiling" ).css( "display", "none" );
// Full code for for h3 element on click
// hide the sibling div element
$(document).ready(function(){
$("h3").on("click",function() {
$(this).next( "div" ).css( "display", "none" );
})
});