Facebook and google?

I came across an anomaly. A cross over of sorts between Facebook and Google, who to my mind were different companies. There is a contact of mine located solely in Google Mail whom has never contacted me other than through email or phone. Somehow, this contact ended up being a Friend Suggestion on Facebook. hmmm. Why would that happen? They shouldn't be affiliated, not to my knowledge. I didn't see anything in the EULA that said they were allowed to acces contacts of the other party (site/domain). Are they sharing databases or something? This seems really odd.