Hello Patricia,
I think the townland you are referring to is Kilrush, located in County Clare. If this is correct, and if your ancestors were Roman Catholic, I found the baptism transcription for a Joseph Sexton in the St. Senan's Catholic Parish, County Clare, on 3 January 1849. His parents are Timothy Sexton and Mary O'Brien. St. Senan's is the variant name for the Catholic Parish of Kilrush.
The baptism transcription for Joseph was found at the Find My Past (FMP) website. You can access the transcription, but you'll first have to register with FMP. Once you register, click on the following link to access Joseph's baptism: https://is.gd/4z8JVI
In the transcription, the father Timothy's name is spelled, "Thimoty."
The baptism of Joseph Sexton is a few years earlier than the birth year you have for him, but this could be your ancestor. You can access a copy of his original baptism record from the National Library of Ireland website at: https://is.gd/AQkYWp
There are two facing pages of the baptism register. Joseph's baptism is on the left-hand page, first entry below the “1st January 1849” subheading. You can enlarge the baptism by means of round icons in the upper center/ right of the screen. The icons are white with green backgrounds. You can also access the full-screen function by clicking on the last icon on the right with the two arrows pointing northeast and southwest.
Joseph's baptism record further shows that his godparents were Tom Crotty and Mary McGrath.
This baptism is only circumstantial evidence that it pertains to your ancestor Joseph Sexton. You would need to locate records in Australia that tell you his father'a name, and his mother's first and maiden names to be sure this Joseph is your ancestor.
I also found the FMP baptism transcriptions for seven more children of Timothy/Tim/Thady Sexton and Mary O'Brien, including the baptism transcription of a Mary Sexton.
The names and years of baptism for the Sexton children are below. All were baptized in St. Senan's Catholic Parish. I've included the baptism of Joseph again so you can see the full chronology of the baptisms from the FMP website:
Martin Sexton, 1828
Biddy Sexton, 1830
Matthew Sexton, 1839
Mary Sexton, 1843
Timothy Sexton, 1845
Ellen Sexton, 1847
Joseph Sexton, 1849
Matilda Sexton, 1851
____
You'll notice there is an eight year gap between the baptism of Biddy Sexton in 1830 and Matthew Sexton in 1839. This is an indication that Timothy and Mary had more children between the births of Biddy and Matthew. The first name Thady is an alternate name for Timothy. For more information about the name Timothy and Thady, go to the Library of Ireland website link at: https://www.libraryireland.com/names/men/tadhg-teige.php
I also looked for the church marriage record for Timothy/Thady Sexton and Mary O'Brien at the FMP website, but didn't find it. I went to the National Library of Ireland website and found that St. Senan Catholic Parish marriages are only available from the year 1829. Their son Martin was born in 1828. I then looked to see if they had been married in another Catholic parish in County Clare, but did not find the marriage transcription at the FMP website.
Patricia, if you think the baptism of Joseph Sexton refers to your ancestor, please let me know and I'll see if I can uncover any further information about the Sexton family in County Clare.
Kind Regards,
Dave Boylan