He's the most important person to the group.

He's the most important person of the group.

Are they same?

Question

He's the most important person to the group.

He's the most important person of the group.

Are they same?

Answer

No, there's a difference. In the first one, he may or may not be part of the group.

Answer

Also, ‘to’ suggests that the person does something for the group. ‘In’ and ‘of’ don’t.

So the most important person to the group might not be the most important person in the group, even if they’re in the group.