Two statements may both be declarative in form and purpose, yet differ so much in topic that no suitable connection unites them. One may describe a person’s stature while another refers to an unrelated state of a different person; their shared declarative form is insufficient to justify coordination.
The “common link” may be rational, imaginative or associative. It must connect the statements for the actual discourse purpose. Merely mentioning two nouns or two actions in one conversation does not establish that link.