Hold the Line allows the character to make an AoO against any opponent that charges him. This would definitely allow him to make an AoO against both
and
Also, for all those that think that
would have got Sneak Attack damage, it is possible, but only if she has the Opportunist special ability, and then only with a single arrow.
Even if she was next to Tarquin and was directly opposite an ally, you can only flank squares that you threaten, and you cannot threaten squares with a missile weapon, only a melee weapon.