Your Liggetts seem to have emigrated to Australia, but apparently Joseph Liggett (the father) returned to Ireland within a few years, since you found his 1870 death record at Derrycreevy. Or was the Joseph Liggett in Australia a different and younger man, perhaps a son of Joseph who died in 1870 at age 83? These aren't my ancestors but I have other Liggett relatives in County Tyrone.
"South Australian Register" newspaper
October 24 1856 - Married on the 14th inst., at Fair View Farm, by the Rev. Robert Haining, Mr. John Marrett, of Altamira Farm, Upper Dry Creek, to MISS MARTHA LIGGETT, third daughter of MR. JOSEPH LIGGETT, Derrycreevy, County Tyrone, Ireland.
August 7 1858 - Married on Wednesday, the 4th instant, at Salisbury, by the Rev. Mr. Boake, Arthur Russell, formerly of Wiltshire, England, to MARGARET, eldest daughter of JOSEPH LIGGETT, Fair River, Dry Creek, formerly of County Tyrone, Ireland.
"Londonderry Sentinel" newspaper (Ireland)
November 26 1858 - Married August 4, at Salisbury, South Australia, Mr. Arthur Russell, formerly of Wiltshire, to MARGARET, eldest daughter of MR. J. LIGGET, formerly of Tyrone.