As far as I know, In Windows, Mac and Ubuntu, there is no default support for having two mouse pointers on the screen. Your best bet is to mess with the core operating system to obtain this. Maybe some third party apps allow you to do so. But I'm curious where would you need it?
We use collaborative working on number of places. If you want to type on a document at the same time, I suggest you Google Drive that helps to work collobratively on its applications. You can add as many collaborators as you want and all of them would be working just fine.
Just visit drive.google.com and sign in with your google account.
1) Create a New Document (Google Doc) or Spreadsheet (Google Sheet)
2) Share the document with the person you want to remotely work with.
3) Start working.
There are many other apps (Google and many others) that support online collaboration and allows multiple users to connect to a single app.