[Jespah]

Hey Tana - how exciting for you all!

Just make sure Rhys does get a bit of extra attention for a little while, but don't change things too much. Feed them at the same time - but feed Rhys first, that will tell him he's the number 1 Corgi still. It will take them time to work out between them which one is the boss.
I think they will be fine. Rupe who is notorious for being rude and not very welcoming to new dogs of any kind, has done very well with Jem. He's shared his toys, although if he's not happy she has something, he'll just go and take it away from her. The only problem was once the second day when he went after her in the car over a piece of doughnut - Rupe is a food guy.
It won't take long for things to work out, Rhys seems very laid back and easy going from all you've told us.
Have fun, take lots of photos!!!