The two events co-occurs frequently.

The two events are co-occurring.

The two events co-occurred last night.

During World War II, the United States and the Soviet Union were co-belligerents against Nazi Germany.

The co-belligerents fought together against a common enemy.

The co-original idea was presented by both authors.

There are many co-dependences in their relationship.

Co-dependence can be a challenging dynamic in relationships.

She co-writes songs with her brother.

She co-wrote the script for the movie.