Is it possible to save a custom Theme with content ?

I have a website with couple of sub sites. Sub sites are password protected and only users can view them. In future there will be lot more sub sites for different users. But all of them will use the same theme and ,80% of contents are going to be same as well. So is it possible to save the theme with contents? Or is there any other ways to use the same content in all sub sites? There will be exclusive contents for each sub sites as well.