For example, it is more likely for identical twins (who have identical genes) both to suffer PTSD after war combat than non-identical twins.
(it; is; more likely for identical twins (who have identical genes) both to suffer PTSD after war combat than non-identical twins) (identical twins; have; identical genes)
it identical twins
is have
more likely for identical twins (who have identical genes) both to suffer PTSD after war combat than non-identical twins
identical genes