SSL Cert interferring with other sites

[SkyBlade]

I'm a little out of my realm here and cannot find answers.

I have several sites on a linux server.
Some Joomla, some not.

I have one custom built CMS site with an SSL cert. (site A)
I have two Joomla sites (site B & C) that I'm finding google links for that are cross-referencing the SSL cert. (B & C do not have SSL certs.)

So, I have URLs I find in google for sites B & C that give me untrusted certificate warnings.
If I go ahead and trust the cert manually and get the page to load, it actually shows site A.
The domain name though, is from site B or C, but the rest of the URL after '.com/' is from site A.
In these odd, cross-bred URLs, it is also using https where sites B & C should only ever be http.
Really strange, making no sense to me.

It's hard to even explain, I hope I'm making sense.
Any feedback to resolve this is greatly appreciated!!!