BGP Route Advertising Question

This is going to be a stupid question I think to a number of you but I want to make sure I fully understand this as I need to explain how this works to someone else to avoid a fight on basic theory/best practices.

So I have router A and router B. Router A is going to eBGP peer to Router 1. Router B is going to do the same to Router 2. This is not setup yet but will be.

We control router A and B and someone else controls router 1 and 2.
Router 1 and 2 are only connected to A and B as there only any access to anything outside there ASN. Ie its there only gateway to the rest of the world.

We leased a /25 to the controller of router 1 and 2 that is part of a larger /22 block.
We are using 2 /30 blocks to peer between routers A and 1 / B and 2.

The controller of router 1 and 2 wants me to advertise the /25 to him so he can then advertise it back to me. But if I advertise the /25 to him via bgp and then he send it back to me I believe that will create a routing loop at his router then back to me etc etc.
Is that correct or am I missing something?

If thats correct then from my understanding he should advertise the /25 to me which I'll accept and that will be entered into my table and I'll summarize the route to a /22 to the rest of the world. How he gets the /25 into his table to send to me is up to him.