Niantic, the company behind the wildly successful Pokémon Go and its predecessor, Ingress, was once owned by Google. It all started in 2010, when John Hanke, the grandfather of Google Earth, was given a task. That task was quite simple, in theory; put some kind of interesting stuff on top of Google Maps. Back then, augmented reality and consumer GPS on phones were in their infancy. Hanke and his team experimented with different applications and ways to implement them and eventually came up with Field Trip, an app that launched in 2012 and was made to help people explore their city, popping up interesting locales, businesses and other points of interest on a map, with the user's location shown via GPS. This was the predecessor to Ingress, which was the predecessor to Pokémon Go.
When Niantic first became a company, it was with the 2010 initiative for Hanke to build something on Google Maps. They were known as Niantic Labs. Owned by Google, they could only spread their wings so far; they weren't as agile as a startup, and didn't have the opportunities to secure outside funding that a startup may enjoy, though they did have Google's backing. When Ingress hit the ground in 2013, it showed that Niantic Labs was all grown up, able to churn out good products and hook users on their own merits, without having to piggyback off of Google's name. While Ingress' popularity was in part owed to Google's partnership, it was clear that Niantic Labs was a capable firm.
In September of 2015, just as Google announced the formation of Alphabet and the spinning off of some of its projects and departments into individual companies, Hanke and his team decided to break Niantic off from Google entirely, rather than become an Alphabet company. Now more autonomous than ever, they were able to begin exploring different avenues for business. This eventually led to them seeing dollar signs in Google's Pokémon themed April Fool's joke, and partnering up with Nintendo to make it real. After a $30 million fundraising round, which Google participated in, Niantic was ready to take on the world on their own. At this point, Google is a shareholder and provides the mapping data that Niantic's creations use as a backbone, and that's about the extent of their relationship.