Inter-book communications

Are you aloud to take characters from one book you write, and them also use them in a different series? I don't know. But, I think I'm going to use some characters from one of my books in The Digger's Daughter. I'm going to use William Clarke, from The Card Players as Nathaniel's uncle. I think that works. That will also help me save the other series of books, because I was stuck with them. So, I hope it works.

Cheerio, peeps!