University of Sussex
Mark, Katharine Mary.pdf (1.99 MB)

Sibling relationship quality: a longitudinal study of twins and their families

Download (1.99 MB)
posted on 2023-06-09, 05:19 authored by Katharine Mary Mark
The overarching goal of this thesis was to examine sibling relationship quality in young twin children, as well as the ways in which this key bond is associated with other familial relationships within the home environment. The three articles included were part of a longitudinal and multi-method study, run by myself and my colleague - the Twins, Family and Behaviour study. Accounts were collected from 282 mothers and 132 fathers of twins, over a two-year time period. Parents completed postal questionnaires and a telephone interview, and observations via Skype recorded them interacting with each of their children. The research was unique, as it employed a number of novel measures and sophisticated analyses that have not yet been used within a longitudinal twin sample such as this. Results showed that, contrary to expectations, no mean level differences emerged when monozygotic twin pairs, dizygotic twin pairs, and non-twin pairs were compared on their sibling relationship quality (Paper 1). Behavioural genetic modelling also revealed that sibling interactions were mainly influenced by the shared environment, common to both children within the dyad, but also by the genetic propensities of the siblings themselves (Paper 1). Using the innovative Preschool Five Minute Speech Sample interview, we found that mothers who expressed more family-wide positive, and less family-wide negative, emotion towards their children reported more positivity within the sibling relationship – even when controlling for questionnaire measures of the mother-child relationship (Paper 2). Finally, opposing the majority of past literature, cross-lagged tests evidenced that earlier positivity within the sibling bond was predictive of later marital satisfaction, and of positivity within both the mother-child and the father-child bond (Paper 3). The implications of the findings include: the generalisability of studies of twins in childhood to the wider non-twin sibling population (Paper 1); the usefulness of maternal speech sample measures in capturing unique variance in sibling relationship quality (Paper 2); and the impact of affectionate sibling exchanges on entire family systems (Paper 3). Future research would benefit from exploring the nature of the relationship between twin brothers and sisters further, using both younger and older children’s reports of their family interactions, within a more ethnically and socioeconomically diverse sample.


File Version

  • Published version



Department affiliated with

  • Psychology Theses

Qualification level

  • doctoral

Qualification name

  • phd


  • eng


University of Sussex

Full text available

  • Yes

Legacy Posted Date


Usage metrics

    University of Sussex (Theses)


    No categories selected