If you’re referring to two separate HubSpot portals, then no, it’s not possible to integrate these, see here: Manage multiple HubSpot accounts
It is possible to upgrade one and the same account, for example, your free account could later be upgraded to the Starter, Professional, or Enterprise tier.
If however you or someone else creates a separate HubSpot account/portal for your company, that is entirely separated from any other account, even if you access it with the same email address.