I have heard that Thomas Girty's wife was murdered, but I don't know any of the details. I think I had heard that she was killed because of being a witch or something, but I could be wrong. I don't recall where I read this. The "History of the Girtys" makes very little mention of Thomas' family and only mentions a daughter named Nancy who married a Gibson and a son named John Girty. It's possible that Thomas had a daughter named Catherine, but I haven't seen many documents regarding Thomas. Did he leave a will?
Lyman Draper interviewed John Girty, Thomas' son in 1846, but he mentions none of his family's particulars, only about Simon Sr. and Simon Jr. It says:
Draper’s interview with John Girty and Simon Munger, September 8- 9, 1846, DM 3S:122-124.
"From John Girty, of Pittsburgh, son of Thomas Girty. – Simon Girty Sr. (father of Thomas, Simon, &c.) was an Irishman, came to America – married Mary Crosby, an English woman; and settled on the Big Island of Susquehanna, below Harrisburg where all the boys, Thomas, Simon, James and George Girty and their half-brother John Turner were born – and captured. John Turner (a child at the breast when captured, died on Squirrel Hill, some five miles from Pittsburgh, May 20th 1840. Thomas Girty was 17 when captured – escaped from the Indians at Kittanning – died at Pittsburgh, in 1819."
"John Girty yields to Captain Murphy’s version of Simon’s escape in 1778 – and to Simon Munger’s (a grandson of Simon Girty) assertion, that Simon was at Crawford’s burning, but could not prevent it, without taking his place."
The will of John Turner as written in the Girty book mentions John Girty and Nancy Gibson as children of Thomas Girty. It also says that Turner left Catherine "Bealer" one dollar, but mentions no relationship. No doubt some sort of relationship here since Turner left all of his estate to the families of his half-brothers.
An obituary for Thomas Girty was published in the Pittburgh Gazette, but the Girty book only makes a partial mention of it. That's about all I know at the moment.
I'll keep an eye out for the catherine connection.