Each familiar deals damage equal to 0.375x Isaac's damage.
This item belongs to the Conjoined set. Collecting three items from this set will transform Isaac into a three-faced version of himself.
Notes
Twisted Pair is very similar to the item Incubus. It provides the same total damage per second increase in the form of a familiar (familiars in this case).
When playing as Lilith or Tainted Lilith, the demon familiars will deal 50% of Lilith's damage each.
Holding the up/down + left/right attack buttons will make one demon go further behind and the other one in front of Isaac.
Because the demons need time to adjust their position while firing, the left\right directional buttons can be tapped to shoot more precise, straight lines of tears.
They don't inherit all effects and stats from the player. See item interactions below to see the small oversights.
Synergies
BFFS!: Twisted Pair's tears deal twice as much damage.
Tractor Beam: Twisted Pair's tears follow the beam.
Friendship Necklace: Causes the Twisted Pair to orbit Isaac, allowing for a more precise firing of tears.
Interactions
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. This is likely an oversight.
Eye Drops: The familiars do not have the staggered attack, stat bonuses still apply.
Eye of Greed The two familiars will also fire coin tears which spend Isaac's coins. Their shot counter is independent from Isaac's.
Sacrificial Altar: Only 1 item pedestal is spawned for their sacrifice, unless they were spawned through Cambion Conception, in which case they will count for two.
Terra + Brimstone/Technology: While Terra + laser items like Brimstone or Technology don't open doors normally, Twisted Pair's lasers can open doors. This is likely an oversight.
Conjoined set. Collecting three items from this set will transform Isaac into a three-faced version of himself.
Incubus. It provides the same total damage per second increase in the form of a familiar (familiars in this case).
Lilith or 
Tainted Lilith, the demon familiars will deal 50% of Lilith's damage each.
BFFS!: Twisted Pair's tears deal twice as much damage.
Box of Friends/
Crooked Penny/
Diplopia: Each additional Twisted Pair will add two more familiars that float farther out from Isaac.
Forgotten Lullaby: Increases the fire rate of Twisted Pair.
Tractor Beam: Twisted Pair's tears follow the beam.
Friendship Necklace: Causes the Twisted Pair to orbit Isaac, allowing for a more precise firing of tears.
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. This is likely an oversight.
Eye Drops: The familiars do not have the staggered attack, stat bonuses still apply.
Eye of Greed The two familiars will also fire coin tears which spend Isaac's coins. Their shot counter is independent from Isaac's.
Sacrificial Altar: Only 1 item pedestal is spawned for their sacrifice, unless they were spawned through 
Cambion Conception, in which case they will count for two.
Terra + 
Brimstone/
Technology: While Terra + laser items like Brimstone or Technology don't open doors normally, Twisted Pair's lasers can open doors. This is likely an oversight.
Tainted Lilith Unlocks 
The Beast Unlocks 
The Binding of Isaac: Rebirth
