A word for an object that contains two evolutionarily related objects

You might be looking for the word progenitor. This word is commonly used to describe a species that gave rise to another. For instance, "Australopithecus is the progenitor of modern hominid species."

Biologists often speak of a "common ancestor" when referring to a species which no longer exists, but from which two or more other species have evolved.

tinyD makes a good point in the comments. "Most recent common ancestor" would be the most precise term.

If I understand you, you might be talking about - evolution branch, more specifically and technically correct - you might be talking about biological classification (see also taxonomic rank).

Specifically apes and humans are both in superfamily of hominoidea (see changes of taxonomy).

a common ancestor

works for a number of similar 'commonality' situations, when the similarities are derived from the same source.