Not sure where my reply went so here we go again.

OP here, it’s my fault for neglecting the detail yes brother will properly check in as my co-guest, register using his passport and stay in one of the hotels. There’s nothing out of ordinary nor illegal about it.

My question solely relates to whether ONE individual can register to stay at two hotels at the same time, for the same duration, in Beijing.

My brother and I need two hotel rooms and I want two sets of elite night credits, that’s all.

Edit: we both have valid visa etc., I thought my question was clear on that... my bad

Due to bad planning, I've been registered (that is, the PSB thing) to multiple hotels in the same city (Beijing) several times. Nobody cared. As uanj suggested, I would imagine the PSB is more concerned with people who are not registered at all.

You wouldn't need a residence permit for it not to matter.

We stay with relatives, we register when we arrive. If a hotel on a side trip doesn't register us we will still show as registered at the relative's place.

That was kind of my point. When you register at a PSB, you are issued a temporary residence permit, though not all PSBs print them out unless you ask them to. Hotels can also print them out...can be useful for people opening bank accounts.