Children whose parents experience high levels of couple distress are at greater risk for emotional, behavioral, and academic problems. This study tests two types of self-help for parenting couples: the OurRelationship program (OR), an online guided program, and couple-focused bibliotherapy (BT), a book-based self-help approach. The investigators will compare these interventions with a waitlist (WL) control group to see which is most effective at reducing communication conflict between partners. They will also examine whether the interventions improve child well-being when problems are present at the start of the study.

A total of 350 parenting couples in Denmark will take part. Eligible couples have at least one child under 18 living at home and report high levels of conflict or relationship distress. Couples will be randomly assigned to OR, BT, or WL. Questionnaires will be completed online before the program, after the program (10 weeks later), and at 3- and 12-month follow-ups.

Children exposed to high levels of couple distress are at increased risk for a range of adjustment problems, including behavioral, emotional, and academic difficulties. These relational burdens can also interfere with adult mental health, the coparenting relationship, and the capacity to provide warm and consistent caregiving. Despite these challenges, many couples delay seeking help until their relationship has seriously deteriorated.

This randomized controlled trial investigates the efficacy of two flexible self-help interventions: the OurRelationship program (OR) and couple-focused bibliotherapy (BT). The investigators hypothesize that OR will outperform BT, which in turn will outperform a waitlist (WL) control in reducing communication conflict-the primary outcome-between baseline and post-intervention. The investigators further hypothesize that any couple intervention (OR or BT) will outperform WL in reducing the impact on child well-being-the secondary outcome-between baseline and post-intervention for children showing such impact at baseline.

Parenting couples (N = 350) with one or more children living at home, who report either high levels of parental conflict or relationship distress, are recruited via municipal family services in 11 or more Danish sites. Participants enroll through an online platform, complete a screener, provide informed consent, and fill out a baseline survey before randomization. Families are randomly assigned in a 1:1:1 ratio to OR, BT, or WL. Online questionnaires are completed at baseline (T1, before randomization), post-intervention (T2, 10 weeks after randomization), and at 3-month and 12-month follow-ups (T3 and T4, respectively).

Dyadic multilevel models, with repeated measures (Level 1) nested within couples (Level 2), will be used to examine group differences in change trajectories across time for continuous outcomes. Including both a BT condition and a WL control allows the investigators to test whether OR offers added benefit over an accessible low-tech self-help option. Apart from the previous pilot, this is the first trial to evaluate OR independently of its developers and the first study conducted outside the United States.

Inclusion Criteria:

• Meet at least one of the two following criteria: (1) Destructive conflict: one or both partners report being a victim or perpetrator of at least one act of physical or psychological aggression in the past three months (see exclusion criteria for intimate partner violence) OR (2) Couple distress: One partner scores ≤11 (1 SD below the Danish population mean), or both partners score ≤13 (0.5 SD below the Danish population mean) on the Couple Satisfaction Index-4 (CSI-4).
• Both partners are at least 18 years old.
• Cohabiting.
• Have at least one child under 18 living at home.
• Reside in a participating Danish municipality.
• Completed the baseline survey.
• Able to read and understand Danish.
• Have internet access and a compatible device (computer, tablet, or smartphone).
• Agree not to engage in couple therapy prior to the 3-month follow-up.

Exclusion Criteria:

• Current plans to divorce or separate.
• Ongoing affair.
• Moderate to severe suicidal ideation.
• Recent incident of intimate partner violence resulting in physical injury or fear for the safety or well-being of oneself or one's children.

The datasets collected for this study are not publicly available due to institutional restrictions at Aarhus University. However, data may be accessed through collaboration with the principal investigator, provided that the researcher is affiliated with a Danish research institution. All analytic scripts and code used in the study will be made available by the authors upon request to facilitate replication.