This is a possibly a sister - Sarah born April 21st 1864 -
LINK see row two #67
parents Richard UPTON and Johanna REARDON of Cloughill
It would imply that 1820 is too early for births to the same couple
There is also a birth in 1879 of an Anne UPTON in Parsonstown - mother Margaret UPTON and informant on civil birth record is Johanna UPTON -
LINKThere is a death for a Richard UPTON in Parsonstown July 28 1896 aged 62; informant his widow Johanna -
LINK #132
This would imply that he was born in 1834 which could be an incorrect age
He may not be the father of Joshua if you are correct with an 1841 date of birth
Johanna UPTON died in Parsonston on Feb 5th 1897 aged 76 -
LINK #203
Being aged 76 implies she was born in 1821
The informant was her granddaughter Hannah Walker
Hannah could have been the daughter of a married daughter to be named WALKER or married herself and therefore born an UPTON or any other surname unfortunately.