[member="Matsu Xiangu"] has been an active presence with the One Sith recently, even taking on several apprentices. In that regard, she is actually more active than Rev.
[member="Logan of Little Coruscant"] is Rev's apprentice and ipsofacto, being training by Rev, has the right to go to any open battle that Rev is involved in. Just because he is a member of the Red Ravens, it doesn't mean that it would get in the way with his activity in the One Sith. In fact, in a way, it kind of makes sense IC. Our relationship (master/apprentice) ties the organizations together and illicits interaction. It muddies the line between ally and active member, but then again, these lines haven't been defined for the purposes of invasions.
If you have questions regarding a One Sith member and their interaction in this invasion, especially if you question the veracity of their presence, feel free to message one of the One Sith Admins. (@Reverance, [member="Darth Isolda"], [member="Darth Helios"]). In reference to these two specific individuals, I discussed the matter with them prior to the invasion and I settled that it would be fine, considering their involvement. If you don't like that, please take that up with me in private and we can sort things out. Just know that I have a rather strict view of it so I take recent activity into full consideration.
Long and short, if you can say with a straight face that said individual is ACTIVE in your group IC, I consider them a member, whether they are a member of another faction or not (and thus do no fall into the ally connotation). But I don't make that decision in a vacuum, I do take the context of the other faction into consideration. Once again, feel free to message me if you have concerns over this.