What kind of heritability estimates (broad sense or narrow sense) are obtained from human twin studies?

Broad sense Heritability.

Explanation:

Heritability is the proportion of variance, in a particular population, that is due to genetic factors and not to environmental influences or stochastic variation.

We have,

Narrow sense heritability’ (h2)which is the proportion of trait variance that is due to additive genetic effects while

‘broad sense heritability’ (H2) is the proportion of trait variance that is due to all genetic factors including dominance and gene-gene interactions.

For twin studies, the total variance can be split up into genetic, shared or common environmental, and unique environmental components this enables an accurate estimation of heritability"

Broad sense heritability is mostly measured for twin due to their genetic components and additivity gene action, environment and most likely cause of difference in case of dissimilarity among Identical twin.

Fraternal or dizygotic twins on average share half their genes (and so identical while monozygotic (MZ) twins on average are twice as genetically similar as DZ twins.

this doesn't support enough information to answer the question.