Survivor and caregiver dyads will receive standard resources and consultations for hematopoietic stem cell transplantation (HSCT) care, which include a joint educational class for patients and caregivers before and after treatment.

Percentage of patients and caregivers who rate the intervention as 4/5 or higher on the 4-item Intervention Appropriateness Measure (IAM) questionnaire (benchmark: 70%). Higher scores signify greater agreement with intervention appropriateness.

The impact of MCP-Dyad on the patient and caregiver's meaning and purpose (increased meaning and purpose equivalent to less existential distress) will be measured using the 48-item Life Attitude Profile-Revised (LAP-R) instrument. It has six domains (purpose, coherence, life control, death acceptance, existential vacuum, goal seeking) that make up two subscales, the Personal Meaning Index and Existential Transcendence. Higher scores generally indicate a more positive attitude towards life.

The impact of MCP-Dyad on the patient's and caregiver's spiritual well-being will be measured using the Functional Assessment of Chronic Illness Therapy Spiritual Well-being (FACIT-Sp) Scale. It has two subscales, one for faith and another for meaning/peace. Higher scores indicate greater spiritual well-being.

The impact of MCP-Dyad on benefit finding will be measured using a slightly modified version of the Benefit Finding Scale (BFS), a 17-item measure that captures positive life challenges resulting from adversity (e.g., personal priorities, acceptance, daily activities, family, world views, relationship, purpose). Higher scores indicate greater benefit finding.

The Mutuality Scale (MS) measures the positive quality of the relationship between the care recipient and the caregiver. Grounded in the concept of mutuality (degree of love, reciprocity, shared pleasurable activities, and shared values) in the patient/caregiver relationship. There is a four-domain structure with items rated from 0 (not at all) to 4 (a great deal) with question stems examining varies aspects of the relationship (e.g., how much do you enjoy spending time together). Higher overall scores indicate greater mutuality.

The Revised Dyadic Adjustment Scale (RDAS) is a self-report measure of relationship quality in couples. It assesses dyadic consensus, dyadic satisfaction, and dyadic cohesion to give an overall index of marital quality. The rating scale is 0 (always disagree) to 5 (always agree). Higher overall scores indicates greater relationship satisfaction.

The Social Constraints Scale measures the extent to which individuals perceive their social environment, particularly close relationships, as a limiting or discouraging their ability to express thoughts and feelings related to a stressful experience. Items are rated from 1(never) to 4 (very often). Higher scores are equivalent to more social constraints in the relationship.

The Communal Coping Domains instrument assesses how patients and caregivers manage health-related behavior change, particularly in the context of health threats by measuring shared perceptions, confidence, and behaviors. There are three tailored subscales: use of communal coping (how frequently dyads use joint efforts to manage health threats), how confident the dyad is in working together to manage health, and beliefs about communal coping strategies. Responses for the use of the communal coping domain range from 1(never) to 5 (very often), and responses for the couple efficacy and outcome efficacy range from 0 (not at all) to 10 (very much). Higher overall scores indicate greater confidence in patient/caregiver coping strategies.

Communal coping can be objectively measured based on the amount of "we versus I" language across the intervention sessions. Linguistic Inquiry and Word Count (LIWC-22) software is a validated way to examine the number of pronouns uttered. Essentially, this software works by comparing each word in a text against an internal dictionary of words and then provides a percentage of total words that fall into a specific category. We will use the recorded sessions to determine the percentage of subjects using plural pronouns.