Here are a few ways that children of OCD parents might accommodate their loved one:
Reassuring their parents to lessen the anxiety they have regarding their intrusive thoughts
Avoiding anything that could trigger their parent's ritual
Participating or even completing rituals on their parent's behalf, such as checking the locks on the doors several times or excessive hand washings
Helping a parent avoid triggers
Making decisions for a parent so they can avoid the anxiety of not knowing the right choice
Modifying schedules or responsibilities to accommodate a parent's OCD