Epic Fetus: Each familiar will fire a missile from a two additional crosshairs. Not Recommended, as the twisted pair crosshairs are not synced to Isaac's crosshair and move at a much slower rate, making self damage much more likely as the additional crosshairs will struggle to make distance from Isaac.
Eye of Greed The two familiars will also fire coin tears which spend Isaac's coins. Their shot counter is independent from Isaac's.
Found Soul: While the soul is alive, decreases Twisted Pair's damage by 20%.