You say "understand", but then rattle off a bunch of facts.

Like knowing hobbies, favorite foods, political opinions, favorite tv/movie/youtube channels/music/genre of entertainment, etc...

No offense, but that's not the same as knowing a person and those aren't the most important things. I don't know the exact right answer to these for most of the people in my life. Hell, I don't know my favorite for every one!

But that's because they're less important. Not completely, but they're just statistics, flavoring on who a person is. I know my sister is endlessly creative and compassionate. I know my mother is fierce and determined, and never gives up on anyone. My father is loyal, dependable, and hard-working. My brother is charismatic and hilarious. My niece is intelligent, tender-hearted, and kind. My nephew is adventurous, inquisitive, and empathetic.

That's who they are, and I know this by spending time with them, through the good and bad times. Assuming they're worthy of it, have you shown your family who you are, your true self? And if they're not worth that, remember that it's only temporary; eventually you can move out, choose your own family and they can know and understand the true you!