Abstract
In childhood, musical play is an important part of home life and, potentially, sibling play. Considering the social‐emotional relevance of musical activities, siblings’ engagement in musical play may also be associated with social development. The current longitudinal study examined musical play in 39 pairs of siblings during naturalistic home play at two timepoints: 1) when siblings were 2 and 4 years old (T1), and 2) two years later when siblings were 4 and 6 years old (T2). Musical play, especially singing and dancing, was more prevalent at T2. Birth order effects were also revealed; 4‐year‐old second‐borns (T2) engaged in more solo musical play than 4‐year‐old first‐borns (T1), but 4‐year‐old first‐borns initiated joint musical play more often than 4‐year‐old second‐borns. Associations between musical play and prosociality also emerged. Specifically, both older and younger siblings’ rates of prosociality correlated positively with older sibling musical play at each timepoint. These findings reveal intriguing effects of age and birth order on both solo and joint musical play between siblings, and highlight a potential link between spontaneous musical play in the home and social development.