If you already know this, fine, but just in case you don't know.... you only have a triangulated group if you share a common segment with two or more others. You might share a 14 cM segment, let's say from 18-32 on chromosome 1, with your known 4th cousin. You might share a 9 cM segment from 21-30 on chromosome 1 with another cousin. You need to do a 1 to 1 comparison on the two cousins to be sure that it's on the same chromosome (you have two chromosome 1s, one from each of your parents). Without doing the 1 to 1 comparison between the two cousins, you wouldn't know if they were matching on the same chromosome 1...