The purpose of this study was to measure fathers' and mothers' linguistic involvements with the development of communication between young siblings. A total of 39 2-parent families with 2 children were videotaped in semi-structured activities in a laboratory setting. The older sibling was from 18- to 26-months-old and the younger was from 4- to 8-weeks-old. Regardless of type of vocalization, when only one parent was present, utterances encouraging sibling interactions were more often aimed at girls than boys, with the result that they occurred more when both siblings were girls than for any other gender combination. Fathers were more active in issuing such utterances, especially to girls. When both parents were present, gender differences between parents disappeared, although the effects of children's gender did not. Overall, the results suggested that fathers very actively direct sibling interactions, especially those involving girls. (Author/RH)