The New Testament comprises a collection of texts related by subject rather than by reference. They don't refer to each other. The Synoptic Gospels are understood to have evolved from an unknown original. Apocrypha are texts that didn't make it into the New Testament as canonized by the Council of Nicea. Parts of Thomas show up in the Synoptic Gospels.

In a big way, the Biblical texts bear similarity to genetic material in the way that copies are generated that are then modified into new functions. The evolution of the basic story content is a slightly different process, where much or most of the content has been drawn from earlier myths, which also evolved through time.

Indeed, religions may be understood to be megamemes that, like a gene-based organism, evolved through time, but are more like cellular organisms that merge or associate symbiotically. I believe that cells originally incorporated mitochondria as a different life form, and that is said to explain the mitochondrial DNA. We can imagine that the proto-gospel of the Synoptic Gospels was written, then copied, and the copies mutated into the four Gospels. These fostered cults that then wrote the Epistles and the Apocrypha. The profusion of texts fostered the Council that blessed some writings as canon, and others, the Apocrypha were banned. Or something like that.