Reviews of behavioral genetic studies note that "control" aspects of parenting yield low estimates of heritability, while "affective" aspects (parental feelings) yield moderate estimates. Research to date has not specifically considered whether positive and negative aspects of parenting--for both feelings and control--may explain these etiological distinctions. We addressed this issue using parent reports of parenting in a large twin sample in the United Kingdom, at ages 9 (N = 2,260 twin pairs), 12 (N = 3,850 twin pairs) and 14 (N = 2,293 twin pairs) years. Our findings supported previous work indicating that parental feelings show greater heritability (h2) than control (across all ages, mean h[superscript 2] feelings = 0.42, control = 0.13). Of specific interest is our novel finding that for control as well as for feelings, the heritability for negative aspects of parenting was greater than for positive aspects (e.g., across all ages, mean h[superscript 2] total negativity = 0.44; total positivity = 0.12). Results across the 3 ages using common pathway models for all scales further endorsed our hypotheses. Previous research has shown that children's genetically driven characteristics elicit parenting; our pattern of our results suggests that what is critical is the "dark" side of these characteristics for eliciting negativity from parents, whether feelings toward the child or control strategies are considered. Improving understanding of how the environment is shaped by the dark side is important theoretically and, ultimately, for targeting intervention.