DO KIDS NEED PPORTS TO TRAVEL TO BELFAST FROM LIVERPOOL AS BELFAST IS CLED AS THE UK?

Hi do children aged 2 & 4 need a pport to fly to belfast, As belfast is in the uk and is cled as a inbound flight Adults only need to provide photo id, We went 2 years ago and only had the 1 child who was 2 and we only had 2 provide a birth cerftifate, but some one told me this has change ???? We are flying with ryan air ???