In my preparation to write to a newly found "cousin", Christie J, I was checking what relationship this man is to me. I'm related to him through his own family line (his grandfather was my 3x great-grandfather, Henry TUCK 1810-1890), as well as through his wife's family (her grandfather was my GG-grandfather, William Walter CLEAVE 1853-1932), both from the Mornington Peninsula area of Victoria.
Checking Ancestry, it tells me that Christie is my "second cousin, twice removed". Fair enough, seeing as we share his great-grandparents and I'm two generations younger than him in the family. So Ancestry recognises my relationship to him but not through his wife at all. In Family Tree Maker (latest version) the Relationship Calculator tells me that he's "the husband of my first cousin two times removed". So it bases our relationship on my connection to his wife, not my connection to him. The trees have been sync-ed (sunk?!) only today, so they're up-to-date and theoretically identical. So according to the FTM description Christie must be my first cousin twice removed, based on my relationship to his wife, compared to being my second cousin twice removed as per Ancestry's calcs.
As for my relationship to his wife, Valma, both Ancestry and FTM calculate it the same: that we're first cousins, two times removed. That's accurate, as we share her grandparents, and I'm two generations younger. No mention of my connection to her husband in their workings.
I'm sure I've confused you all with the cousins/removed explanations, but my point is that two different programs calculated totally different relationships for the same people, using the same data. Weird!