Important update to 23andme the only testing company who does this.. Ron and Peter shown here.. and at bottom Carol and myself
The X is particularly telling for brothers
We’ve updated DNA Relatives and Share and Compare to show full and half-IBD (identical by descent) segments of DNA. You can see completely identical (purple) and half-identical (pink) segments on the Compare page, which you can access by clicking on any of your DNA Relatives matches, or on any of your sharing connections in Share and Compare.
You won’t share fully-identical segments with all of your matches. Full siblings share a combination of fully-identical (purple) and half-identical (pink) segments. Fully-identical refers to stretches of the genome where the two siblings match each other on both pairs of the chromosome - both siblings inherited the same segment of DNA from both their mother and father. The relationship pictured is between two full sisters. Since half-siblings only share one parent, they will only see half-identical (pink) segments.
March 16 update: Full and half-IBD segments are now also shown in the DNA view of DNA Relatives