Findings are reported from Phase 2 of a longitudinal study of family functioning in heterosexual-couple families with 5 year olds conceived using identity-release egg donation. Seventy-two egg donation families were compared to 50 in vitro fertilization (IVF) families (ethnicity: 93% White British) using standardized observational, interview, and questionnaire measures. There were no differences between family types in the quality of mother-child or father-child interaction, apart from lower structuring by fathers in egg donation families. Egg donation mothers and fathers reported higher levels of parenting stress and lower levels of confidence and competence than their IVF counterparts. Egg donation mothers reported lower social support and couple relationship quality, greater anger toward their child, and perceived their child as more angry and less happy, compared to IVF mothers. Egg donation fathers showed greater criticism and anger toward their child, less joy in parenting, and were less satisfied with the support they received, than IVF fathers. Children in egg donation families showed higher levels of externalizing problems than IVF children as rated by mothers, fathers, and teachers, whereas they were rated as having higher levels of internalizing problems by teachers only. Externalizing problems were predicted by mothers' lower initial social support, steeper increases in parenting stress and greater concurrent criticism, whereas internalizing problems were associated with poorer initial couple relationship quality as rated by mothers. Both were predicted by fewer gains in reflective functioning. There was a moderation effect such that parenting stress was a stronger predictor of externalizing problems for egg donation than IVF families. (PsycInfo Database Record (c) 2023 APA, all rights reserved).