Note Prif Weinidog can refer to the "First Minister" (of Wales) or the "Prime Minister" (of the UK). If you need to clarify you can say Prif Weinidog Cymru or Prif Weinidog y Deyrnas Unedig respectively.
Thanks, this had begun to confuse me, beginning to read the news in Welsh. In related news, is "Aelod Seneddol" only "Member of Parliament" or also "Member of the Assembly"?