>>111479309Depending on how you look at it, even he didn't truly follow it. In the EU, he had Maul while Plagueis was still around.
In canon, he was apparently working with Dooku even before Maul was around, though we don't know the full story there just yet. Plus even when he did have Dooku as his official apprentice, he was already grooming Anakin to replace him.
The takeaway seems to be that the Rule of Two only applies if you officially declare a Sith apprentice. This is also how Dooku got away with having Ventress, since he was clearly training her to be the new apprentice once he became the master but he never officially appointed her as a proper Sith. Sheev naturally called him on this.
