We test the hypothesis that parents who conceived twins by assisted reproduction technology (ART), but experienced loss of one twin, have a different parental–child relationship compared with ART parents following a singleton pregnancy. We used the 1994–2005 ART database of the Centre for Infertility of the Arcispedale Santa Maria Nuova in Reggio Emilia, Italy to identify families of 53 singleton births after the ‘vanishing’ twin syndrome. The controls comprised 106 families who conceived and delivered singletons, matched for gestational age (≥ 28 ≤ 31, ≥ 32 ≤ 36, ≥ 37 weeks), maternal age (< 35, ≥ 35 ≤ 40, > 40 years), child's age (1–3, 4–6, and 7–11 years) and child's gender. We completed 3 tests: a sociodemographic questionnaire, the QUIT — Italian Questionnaires of Temperament — motor scale, and the Child Vulnerability Scale. We found that children in the study had significantly more difficulties at the beginning of nursery school (p = .002) and kindergarten (p = .0005), with more frequent anxiety of separation from the parents (nursery school, p = .009; kindergarten, p = .001). We found a lower mean QUIT motor score for the 7- to 11-year-old children when compared to the general Italian normative values, suggesting that parents perceived their children as having more motor difficulties. In contrast, analysis of the Child Vulnerability Scale showed that significantly more parents (15.1%) from the controls perceived their child as vulnerable compared to those from the study group (3.8%), p = .034. We conclude that despite the perceived motor difficulties and the difficulties in the process of individuation–separation that appear at the beginning of the different educational circumstances, parents of singletons following the ‘vanishing’ twin syndrome perceive their children as ‘invincible’, and thus less vulnerable compared to controls.