Four of the witnesses selected for the Editio Critica Maior of Mark are witnesses to a unique combination of catena commentaries on the Gospels not found in any other manuscripts. An analysis of their text in the Gospel of Mark, using the tools of the Coherence-Based Genealogical Method, shows that they also feature an almost identical form of the biblical text that frequently diverges from both the Majority Text and all other Greek New Testament manuscripts. These four manuscripts, GA 238, GA 377, GA 807 and GA 1160, therefore, constitute a group within the textual tradition of the Gospels. This article provides the evidence that GA 377 is a direct copy of GA 807. No other instances of direct copying can be proven within the group, but their agreement raises the possibility that they are siblings. The format of the catenae may explain the high degree of homogeneity in this group of Gospels manuscripts.