PL/pgSQL IF Statement

DO $$
DECLARE
    brother_age Integer := 20;
    sister_age  Integer := 23;
BEGIN
    IF brother_age > sister_age THEN
        RAISE NOTICE 'Brother is older than Sister';

    ELSEIF brother_age < sister_age THEN
        RAISE NOTICE 'Sister is older than Brother';

    ELSE
        RAISE NOTICE 'Twins';
    END IF;
END $$;