If you are a good project manager, can you also be a good change manager or even better?

Certainly must be a change for the benefit of the project in all cases

It depends, really. There are project managers who dealt with big changes in the organisation, these can become change managers, as they experienced it. There are some project managers who don't deal with cultural and change aspects, as their projects might not impact a big chunk of employees, therefore, they would not develop the skills and expertise to become change managers, even though they have the major skills needed, which are communication and stakeholder management

To be a good project manager, you must be have a skill to be change manager

No project is immune to changes. In fact, change management may represent more than 50% of issues, depending on its size, its complexity, how well the requirements have been described by the stakeholders, and how well they've been captured and represented by the analysts.

Agreed with colleagues answers

A project manager better understand change management to ensure succefful implementation of projects and I see that he/she can be good change managers.