I'm going to try to clear up some confusion, and I apologize that this is going to be long. First of all, prior to 1842, no marriages were allowed in the Methodist church, so people had to get married in Church of Ireland churches. Some Methodists allowed baptisms early on, but not all. Baptismal records for Methodists are few and far between early on and they are generally not online. Which means you'd have to visit an archives somewhere to find these records or hire someone to do it. The records I have are mainly from what I can find online and some are from another researcher collecting those records when they visited the RCB at Dublin a few years ago. This researcher collected any Swayne records they could in certain parishes that were of interest to them and to myself. Not all parish records were looked through because of lack of time and generally speaking, they are transcripts not copies of the records. Having said that, this is what I have and keep in mind I have not done a great deal of research of the Clendinnens, but only as they connect to the Swaynes.
John Clendinnen married Mary Ann Ellis in the Diocese of Kildare in 1802. This record is available here -
http://census.nationalarchives.ie/reels/dm/IRE_DIOC_007246535_00057.pdf This record is just a book of Marriage License Bonds and not the actual marriage record. If those records do exist, they are not online and would have to be searched for at the RCB in Dublin.
I do not have birth/baptismal records for any of their children and I do not have a death record for Mary Ann. There are other records that state the two sons I have in my tree (John and William) were born in County Cork. I have no further information on them until they married. I have no further information on whether or not John and Mary Ann had any other children besides those two.
John Clendinnen married Mary Charlotte Robson in the Diocese of Ossory in 1813. Here is that record -
http://census.nationalarchives.ie/reels/dm/IRE_DIOC_007246537_00138.pdf. This record also includes Mary Charlotte Crane marrying Middleton Robson in 1797 and Mary Cecilia Robson marrying John Swayne in 1818.
I have no records for any children they might have had. The Gorey parish records don't start until 1827 and the first Clendinnen in those records is a grandson named Joseph born in 1828. The Newtonbarry parish records are available online at the RCB (google Anglican Record Project). There are a few other parishes available as well. The only Clendinnen record in the Newtonbarry parish records is William's marriage to Lydia Deaker.
Middleton Robson and Mary Charlotte Crane were married in the Diocese of Ossory in 1797. Middleton Robson died in 1798 on Wexford Bridge. Mary Charlotte Robson then married John Clendinnen in 1813. It is unknown if they themselves had children. What I have right now is that John Clendinnen had two children with his first wife, Mary Ann Ellis, and Mary Charlotte Crane had one child with her first husband, Middleton Robson. It's possible there were other children, I just don't have records for them at this time. Mary Cecilia was John Clendinnen's step daughter, not his daughter and I have no records that state he had any biological daughters at all.
I do have the transcript of John Swayne and Mary Cecilia Robson's marriage. It states they were both from Newtonbarry and that they married in Enniscorthy on 26 July 1818. They are listed in the Methodist Class books from 1819 to 1831. I have a memorial of a deed that places them in Carley's Bridge in 1832. There aren't any baptismal records for any of their possible children available online. Possible children are Elizabeth, born about 1821, Mary Charlotte born about 1822, William Middleton born about 1825 and Anna Cecelia born about 1825. It's possible they had other children. John Swayne died 27 Aug 1847. I don't have a death record for Mary Cecilia.
I, personally, do not have any records that state what John Swayne's profession was. It is however possible that he was both a yeoman and a merchant. It is also confusing as to why in the announcement for Mary Charlotte Swayne's married to Thomas Brend that she is referred to as John Clendinnen's niece. I don't have an answer for that.
I have also realized that many researchers appear to have Mary Ann Ellis and Mary Charlotte Crane/Robson confused and/or combined. They also appear to have placed Anna Cecilia Swayne as their daughter and not their grand-daughter, which is why there is confusion about "Cecilia Clendinnen". This is why it's really important to take what other people have in their trees with a grain of salt. Many people get so far into something and then don't do follow up. I think this is also why there is confusion about a son named Samuel, who I haven't found any records of. The person that put them in their tree cites no sources of where this son was supposedly born. I would suggest you ignore what other people have in their trees unless they have a record to back it up and in this case, they don't.
I hope this has cleared up some confusion.