They don’t need to read your messages. Your behaviours outside of the messages are enough and they fact that you messaged each other. Some simple explanations

They don’t need to read your messages. Your behaviours outside of the messages are enough and they fact that you messaged each other. Some simple explanations from there on out: - your partner searched for the bike service or just any bike services and they happen to be the best fit for ads. More so, if you mentioned it to any friends, they could have searched for it and Facebook can associate relationships. - neither of you may have had an original thought when the discussion of using the service came up. You maybe heard the idea in passing and/or were in an area where others were searching for it. Facebook doesn’t need to know what you talk about, as much as they need to know who you talk to and building relationship models from there. Everything after that is simply extrapolating that you have interests similar to the people you interact with regularly OR to the people who go to the same places as yoy