Final answer:
The estrangement between Alex, Simon, and their father would fall under emotional factors that influence a family system's response to death.
Step-by-step explanation:
When examining the estranged relationship between Alex and Simon and their late father, the situation described would most closely fall under the emotional factors that can influence a family system's response to death. Emotional factors encompass the feelings, attachments, and connections between family members. The estrangement in this scenario is a result of the brothers' emotional responses to their father's actions—his divorce from their mother and his remarriage to another woman. It represents unresolved feelings and possibly a lack of closure that could significantly affect how they cope with his death.
Religious beliefs, mentioned in the reference material, can provide hope in an afterlife and social support, which could facilitate coping with death. However, in the scenario with Alex and Simon, it is not the religious but rather the emotional underpinnings that are impacting their response to their father's passing.