I assume you're referring to the 'Catchweb Spidershrine' ability:
Add 1 to casting and unbinding rolls for friendly SPIDERFANG WIZARDS while they are within 12" of any friendly models with this ability.
The ability doesn't care how many models with the 'Catchweb Spidershrine' ability there are. As long as there's any within 12" then they add 1 to the casting and unbinding rolls.