This study examines the mother-reported language practice in bilingual English/German-Norwegian, two-parent families in Norway, and explores the effects of (1) parental input patterns, (2) parental gender, and (3) status of the heritage languages (HL), on success of HL transmission and on children’s language use with siblings when the children were age five. Using mother-reported questionnaire data from the Norwegian Mother and Child Cohort Study (MoBa; a national birth cohort in Norway), we collected information about the languages spoken by the children and the home language use of 204 English-Norwegian and 99 German-Norwegian families. The success rate of HL transmission was reported to be 79.9% in English-Norwegian families, and 72.2% in German-Norwegian families. However, less than half of the bilingual children interacted in HL with their siblings. Different parental input patterns were found to have different effects on HL transmission and on children’s HL use with siblings. Additional HL input from the Norwegian parent seemed not only to promote HL transmission, but also increase the probability of children’s HL use with siblings. Mothers being the HL user was associated with higher rates of HL transmission and higher rates of children’s HL use with siblings.