Merging two on premise domains (Primary and routable domain) to office 365 domain

[Fred_Kyei]

Hi , i have a client who wants to merge two on-premise domains to a domain in office 365.

can this be possible? 

If yes, kindly share how it can be done.

thank you.

[#2]

You need to add both domains to the same office 365 tenant! There can only be one Ad connect to a single tenant , so if you need sync, either consolidate Ad’s or create a trust so accounts can be synced from one Ad connect from both domains! Also set all accounts to the routable domain UPN in both AD’s

[#3]

Adam, multi-forest sync to a single AD tenant has been supported for years now: https://docs.microsoft.com/en-us/azure/active-directory/hybrid/plan-connect-topologies#multiple-fore...

But I'm not so sure what the OP means here, so lets wait for additional details.

[#4]

Of course it have :) was thinking the other way around! Sorry

https://docs.microsoft.com/en/azure/active-directory/hybrid/plan-connect-topologies