Belong to means ownership or possession:
▶️ That’s my bike. = That bike belongs to me.
▶️ This is Kate’s jacket. = This jacket belongs to Kate.
▶️ That’s our neighbors’ dog. = That dog belongs to our neighbors.
Belong with means that things/people are similar and should be together. If one
person in a romantic relationship says “You belong with me,” it is like saying that it
is destiny for the two people to be together.
You can also use belong with or belong in for putting an object into a category with
other, similar objects:
▶️ That book about humans traveling to Mars doesn’t belong in the history
section. It belongs with the other science fiction books.
An object belongs IN a category, and belongs WITH other similar things.