The Irish civil indexes show two possible matches. There’s a marriage between Daniel Kelleher and Julia Sullivan registered in Millstreet, Co. Cork, in 1871 Volume 5, page 658; and another between a couple of the same names also in Millstreet in 1872 Volume 5, page 611. The first marriage appears to have taken place on 21.2.1871, the second on 8.2.1872. A son Daniel was born on 20.1.1872 to a couple of those names.
I would send off for the certificates to see what information they contain.
Here’s a Daniel & Julia Kelleher in the 1901 census of about the right age. Trouble is these are common names. There may be no connection: