Can I use my 2 year membership on more then one computer?
what is membership?do you telling about license?
Welcome to the forum. 
Only if your license was purchased for multiple computers.
Need to know which product you’re talking about.
Also, if it’s a paid-for license, is the question, “Can” or “Should”?
I would concern yourself with your own avast license.
He is a known thief! :
Would not surprise me if he is using a pirated operating system as well. 
Can we please stay on topic in helping natecc’s problem.