Do I have to disclose personal information to the new owner that I never gave the old one?

It depends on what's being asked for and why, rather than a flat yes or no. A new owner stepping into the role of employer has a legitimate need for certain baseline information to actually run payroll, benefits, and statutory compliance properly — this can reasonably include things like updated banking details for direct deposit, emergency contact information, or confirmations needed for tax and benefits administration, even if the old employer handled some of this differently or informally.

What you're not generally required to hand over is information unrelated to actually employing you — details that go well beyond what's needed to run payroll, administer benefits, or comply with legal obligations, especially anything that feels more like idle curiosity than an operational need. If a request feels excessive relative to what it's actually for, ask directly why the new owner needs that specific piece of information and how it will be used and protected, rather than assuming you have to comply with any request simply because ownership changed.

Reasonable administrative requests during a transition are common and usually fine to provide; requests that seem disconnected from actually employing you are worth questioning before you hand anything over.