It's been 3 weeks since I picked up a stray cat

I was worried they might fight with my existing cat,
so I was planning to foster the new one
and then find it a permanent home elsewhere,
but my current cat treats the new one like its own child.
A cat's maternal instinct is truly amazing.
Seeing how well they get along,
I feel like I made the right decision to bring it home.
On the other hand, my existing dog seems to be feeling a bit left out,
so I plan to manage the hierarchy with the dog as the top priority.