Maree:
I searched for a marriage record for Michael and Ellen on the subscription site Roots Ireland but I did not locate a marriage. As you likely know many RC parishes in Ireland do not have records back to 1820 and earlier. Loughglynn records begin in 1817 so a baptismal record for Michael Barrett would not be available.
I did find the three baptismal records for the children you highlighted in your message.
Roger McDonnell