Key points are not available for this paper at this time.
Lise M. Youngblade, Judy Dunn, Individual Differences in Young Children's Pretend Play with Mother and Sibling: Links to Relationships and Understanding of Other People's Feelings and Beliefs, Child Development, Vol. 66, No. 5 (Oct., 1995), pp. 1472-1492
Youngblade et al. (Sun,) studied this question.