His many distinguished pupils included Pierre Boulez , Karlheinz Stockhausen and Yvonne Loriod , who became his second wife .
He was also a great music teacher who taught several young students who became well-known composers e.g. Pierre Boulez , Yvonne Loriod ( who became his second wife ) , Karlheinz Stockhausen , George Benjamin and Iannis Xenakis .