Can I have three domains as one multisite

I want to create new multisite within 30 subdomains and I need also create new 2 different multisite for example 1 for blogging and 1 for forums, I mean my clients can create their blogs and their forums as subdomains . Can I make all these multisite to be one domain or at least one site with three domains. I need all of them to be as one big site.