With respect to the influence of age, both longitudinal research conducted by Dunn et al. (1999) in the United Kingdom on an ethnically diverse sample of over 3,500 early-adolescent sibling dyads, and cross-sectional research mentioned earlier conducted by Stocker et al. (1990) found that older adolescents are less likely to report conflict with their siblings than are younger adolescents and children.
Cross-sectional research conducted by Buhrmester and Furman (1990) found, among the 363 middle- to-upper class early to late adolescents sampled, that the older the siblings were in the sibling dyad, the less conflict the younger sibling reported with the older sibling. Their findings suggest that sibling relationships become more egalitarian with age. Similarly, cross-sectional research conducted by Stocker et al. (1990) found that the larger the difference in ages between two siblings the more likely they were to be rated as having a positive relationship while being viewed during a video-taped session.