This breed will probably take charge of a less dominate dog. Depending on how old and timid your King Charles is he/she may or may not like having a new partner.
i have shih tzu and german sheapered they get along good but it took a while to get along
We have a 3 yr. old male shih tzu. He is definitely an alpha dog. We would like to get a second dog, and are researching which breed may complement him.