Paul A and Paul F are half-brothers of Paul D. It's hard to tell these two apart because we barely hear about them and because they share the same first names—which, of course, is the point. Slavery was so demoralizing and dehumanizing that the Pauls never even got separate, distinct first names.
Mr. Garner bought all three Pauls when they were young, but Mrs. Garner sold Paul F to another slaveowner at a place called "the trace" in order to keep the plantation financially afloat after Mr. Garner's death. In the end, Paul F is one of the reasons that Paul A and Paul D dither about escaping with the rest of the Sweet Home crew. They can't decide whether to go get Paul F to join them (they eventually decide not to).
At the same time, Paul A is one of the main reasons the Sweet Home men decide to escape in the first place. Schoolteacher beats Paul A—a first for the group, who've had it pretty good at Sweet Home up until schoolteacher replaces Mr. Garner. And Paul A becomes one of the casualties of the big escape. He never shows up at the designated spot, and Sethe suggests that he was hanged, with his head and feet cut off (19.198).