Is your former sister-in-law Cheyenne, by any chance? In'The Honor of Arms', by Charles Convis, a biography of Myles Keogh,there's a quote from one of his letters home to his brother Tom. He says how pretty the Cheyenne girls are (he wasn't being un-PC, he called everyone 'girls'!) -- and casually mentions that he's living with one of them.He describes her as 'very intelligent'.
Interestingly, he says that other officers on the post 'have two or three about them', whereas he's with just one. He was a great one for falling in love, so it was probably a real, loving relationship rather than an exploitative thing. It'd be nice to think so; he seems to have been a very sweet man.