Say that a pair of dizygotic twins is discordant for smoking. (discovermagazine.com)
We applied sibling fixed - effects models to same - gender dizygotic pairs (n = 509 pairs) because they are no more alike than ordinary siblings (with the added advantages of being the same age and gender). (pnas.org)
19 Table 5 documents that the number of monozygotic twin pairs concordant for transsexualism is greater than that of dizygotic twin pairs. (acpeds.org)