That was a bit of a shocker. Ike raised by a group that would later be called JWs? JWs mining the relationship (via mum)? Whoa. I took an extremely brief look at the "River Brethren" which is/was the official story. Extremely brief. As in, I failed to notice they were Anabaptist. D'oh.
In reading Dyck's _An Introduction to Mennonite History_, I stumbled across a section on the Brethren Church/Dunkards/River Brethren and I Remembered Ike's Mom. Holy Moly. Another Mennonite become JW.
If I didn't know several people who went from JW to LDS, it would have taken me weeks to recover. As it was, my exploded brain cells reassembled themselves efficiently and I was moving right along again within 24 hours.
In the meantime, however, I'm wondering about Charles Taze Russell. I know there is massive overlap between JW eschatology and Seventh-Day Adventist eschatology (and I understand there was extensive interaction between adventist groups and Russell early on). I'm a lot less clear on Mennonite/JW connection, but thinking that the River Brethren (with their emphasis on immersion) are a likely candidate. Russell being in Pennsylvania presents a target rich environment for Mennonites of all flavors as well. Initial googling doesn't turn anything up, but with this topic area, it never seems to.
ETA: It took a while, but while I've got nothing on the Mennonite/Russell theory, I _do_ have something connecting Christian Church (Disciples of Christ) to Russell: the Emphatic Diaglott (Wilson was connected to Stone-Campbell until he decided to co-found another group). This isn't significant to anyone but me; my Repeatedly Religious G'ma had extended family in Stone-Campbell/Disciples of Christ then married a guy who was raised Mennonite then converted to JW. A connection between religion #1 and religion #3 is personally satisfying.
I was also interested to stumble across indications that pre-White adventists were mostly anti-trinitarian.