Hi, sorry for the lack of clarity--it would be T = environmental component specific to twins, which can be obtained also if siblings are included in the analysis (as an extended analysis): https://doi.org/10.1093/cercor/bhaa254.
As a comment, note that variance that seems specific to twins because DZ twins correlate more than siblings could be due to age and cohort effects that decay the sibling correlation relative to the DZ twins. Even prenatally, maternal diet and stress likely differ more across pregnancies than it does across placentas in a twin pregnancy. That too could easily generate lower sib than DZ correlations. These processes seem inherently at least as likely as, e.g., people going "Ooooh they're twins, let's treat them really really similarly..." - this is especially difficult to do if you don't know a person is a twin :).
Hi: Not sure I understand what you are asking: What is the "twin variance component" to which you refer?
Hi, sorry for the lack of clarity--it would be T = environmental component specific to twins, which can be obtained also if siblings are included in the analysis (as an extended analysis): https://doi.org/10.1093/cercor/bhaa254.
Might there be any insight into this, or would it be more appropriate to use openmx directly specifically for this question?
As a comment, note that variance that seems specific to twins because DZ twins correlate more than siblings could be due to age and cohort effects that decay the sibling correlation relative to the DZ twins. Even prenatally, maternal diet and stress likely differ more across pregnancies than it does across placentas in a twin pregnancy. That too could easily generate lower sib than DZ correlations. These processes seem inherently at least as likely as, e.g., people going "Ooooh they're twins, let's treat them really really similarly..." - this is especially difficult to do if you don't know a person is a twin :).