Can you use grapple combat maneuver while grappling to grapple two creatures at once(if you can also maintain the first one of course).
I ask this as the style feat Grabbing Style says you can grapple one-handed without penalty and further the two following feats both mention grappling two creatures with the style feat(the first Grabbing Drag saying that you can't do its thing if you are grappling two creatures and the second Grabbing master saying that "When you are grappling two opponents using Grabbing Style..." continuing by saying the extra thing you can do with the Master feat).
So none of the feats say that 'that' feat would let you grapple two creatures but the second two very clearly suggest or don't even work without grappling two creatures.
I also know of the -20 thing in grab ability however the penalty is to ignore grappled condition, it does not say anything about grabbing multiple creatures.
I would like an official answer if that is possible.
According to what the rules say, there is no stated limit I have found as to how many people you can be in control of a Grapple with.
In practice, it's very hard to be in control of multiple Grapples opponents at the same time.
Normally, Grappling is a Standard Action.
Greater Grapple lets you make a Grapple Check as a Move Action, but not to Initiate a Grapple.
Grab lets you Initiate a Grapple as a Free Action, but only Initiate.
Hamatula Strike lets you Grapple for free as part of an attack with a Piercing Weapon, and then Grapple to Inflict Damage.
My understanding is that with Grabbing Style and Greater Grapple, yes, you can grapple (and maintain) against two opponents at a time. It is, as Scott notes, still a standard to initiate the grapple, unless you have some other ability.
Snapping Turtle Clutch would let you start a grapple off turn as an immediate action, but then you’re talking about needing something else to let you have two styles active at once.