Two weeks after Umno likened the formalisation of its cooperation with PAS as their "wedding ceremony", the Islamist party's chief said such a union would be incestuous.In fact, the relationship between the two parties is more like that between siblings, PAS president Abdul Hadi Awang said during a public discourse programme on Malay unity at Universiti Malaya Alumni Association's clubhouse in Kuala Lumpur last night.