Can the thread ID of a multithreaded process be the same as the process ID of another running process?

I'm trying to find a way to uniquely identify threads in a multi-process environment. I have a server that keeps track of the different processes connecting to it, some of which are multi-threaded and some of which are not. To identify the threads from multi-threaded connections I'm using the thread ID as a unique identifier (there will be a maximum of 1 multi-threaded process connected at any given time). My question is: is it possible the thread ID of one of these threads could be the same as the process ID of another processes running on the system?

Thanks in advance for the help!