Direct Connect is provisioned in one of the accounts (Network account) How to share DX to different AWS accounts

For most basic setup

You need to create Virtual Interface and mention other account ID in it.

Please check steps here

https://docs.aws.amazon.com/directconnect/latest/UserGuide/create-vif.html

Create a private virtual interface For Virtual interface owner, choose Another AWS account, and then enter the AWS account.

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A better/alternate approach will be. Create DX Gateway in your Network Account. Created VIF on DX Gateway in your Network Account. Then attach cross account VGW with your account DX Gateway

Again use same document link as above For Gateway type, choose Direct Connect gateway.

And use below document to connect cross account VGW with this DXGateway and it can use the virtual interface to reach on prem.

https://docs.aws.amazon.com/directconnect/latest/UserGuide/multi-account-associate-vgw.html

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Most Advance option is using Transit Gateway. But its usually preferred if you want VPC to VPC communications as well.

This document is good for overall understanding of different options.

https://d1.awsstatic.com/architecture-diagrams/ArchitectureDiagrams/hybrid-connectivity-to-transit-gateway-ra.pdf?did=wp_card&trk=wp_card