Yes, it's possible.

Route-reflector are often needed when you have multiple iBGP routers and they aren't fully meshed.

For instance, You have router 1 and 2 directly connected to router 3 in full meshed. Then you have router 4 connected to router 5 and router 6 in full meshed. Router 3 and router 4 are connected to each other. Router 3 can route-reflect in behalf of Router 1 and 2 while router 4 can route-reflect in behalf of router 5 and router 6.

HTH,

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Edison.