General synonyms:
* Entangled
* Interconnected
* Linked
* Connected
* Combined
* Woven
* Braided
* Interlaced
* Merged
* Integrated
* United
More specific synonyms:
* Interlaced (for things that are crossed or interwoven)
* Embraced (for things that are closely connected)
* Inseparable (for things that are impossible to separate)
* Interdependent (for things that rely on each other)
* Synonymous (for ideas or concepts that are closely related)
* Intertwined fate (for things that share a common destiny)
The best synonym will depend on the specific situation and the meaning you want to convey.