Futher records to piece together their lives are tax records, registries (like doing inventories for the government) and you have guilds and orders who wrote things down. From simple bookkeeping to extensive chronicles. If you are lucky you have early authors and artists describing the locale. Even better are judicial records which tend to be exhaustive and on the whole quite accurate in description. Often noting the exact words of the of ones involved. Also there are a ton of objects surviving. Just go to your local antiquarian and be ready to dive into the world of our ancestors.
All in all you get a pretty good picture of your ancestors lives and context they lived in.
While knowing is a personal accomplishment, and you can go through lengths to verify all by yourself, some sources can be trusted and create a bedrock of knowledge. Like if you know C# you don’t have to go and verify if every command works as described. You trust the authors and you know it was done with rigor.