Can we have the engine source in our project git private repository?

We´ve made some simple changes to the engine source so we tought that the best way to make it practical is to have the engine source in our project repository.
Are we allowed to do that? We´re 3 developers with access to the repository and each one have an Unreal Engine subscription

Thank you!

Yes, this is totally fine. You are allowed to store engine source in your own source control as long as only other active subscribers have access.