I imagine Google do know.
If you use Google they log everything you do and every piece of meta data they can get their hands on which likely includes your IP address, browser meta data and so on. (These days that includes things like - what fonts are installed on your PC, how your audio drivers behave, timings, OS version.. everything they can collect so that they can still tell it's "you" whether or not you've cleared your cookies, deleted your browser history, recited the mantra and logged out of all services. Google Browser Fingerprinting and read some of the university papers on it if you want to be really frightened!)
When you browse from another device in your house
some of that meta data will certainly match (IP address, for one) and they'll use that to determine it's probably "you" and serve you ads for things you've searched for.
Google do it, Facebook do it, Youtube do it, Yahoo do it.. anyone providing a service for 'free' will do it.
If you don't like it - don't use the internet! Definitely don't use any major search engine - try Duck Duck Go, who do no tracking.
Of course, that won't help you when most websites use Google AdSense and/or AdWords for their advertising, of course, which means Google still get to know what sites you've been to, even if you never visit Google.
There are steps you can take to prevent that - like installing something like Privacy Badger, HTTPS Everywhere, maybe AdBlockPlus or whatever the equivalents are across
all your devices to block Google tracking cookies (and many other companies doing the same thing).. but unless you're technically savvy I'd suggest putting up with it