The phrase "to know the person" means to have a deep understanding and familiarity with someone, including their personality, feelings, and experiences. Full definition
Similar and related words and phrases are presented below.
As a person who knew people who died and families who lost loved ones, I can very safely tell you that it does not seem like 10 years. (religion.blogs.cnn.com)
That's just not realistic, and I honestly don't know any person who does that. (glassofglam.com)
In this way, you will be interested in knowing the person in a better way and thus, can have success in online dating process. (jumpdates.com)