I have a question about an unknown IP addresses?

My virus software keeps alerting me of an unknown IP address connecting at random to my network. The IP address is 192.168.0.102 I searched and found this might be a "static IP address" a term I dont fully understand. I have checked off my router, my pc, and my wife's mac for their IP addresses. Is this additional IP address something I should be worried about? I have marked it as an intruder, but that does not seem to prevent it from connecting every 5-10 minutes or so. Anyone who knows more about this would be a great help.