The inheritance patterns for the X chromosome for males and females is different. Men inherit only one X chromosome, from their mother, while women inherit two Xs, one from their mother and one from their father. In turn, their parents inherited their X in a specific way as well. All ancestors don’t contribute to the X chromosome. See this link for a really decent primer on X-DNA.
The chart below shows how I (and my brothers, my father) inherit X-DNA. You can see it only comes via specific ancestors. So those are the lines to explore if we have an X-DNA match.
Also, check out the information about DNA testing and results
This is what an X-DNA inheritance line looks like for my sisters and my mom. There are of course a lot more lines where the X-DNA can come from but there are ones where it can’t. By looking at the X-DNA between siblings, it can be possible to determine if a match is on mom’s side, dad’s side or maybe they share a common ancestor and what lines to ignore.