I have just found out that my parent is having an affair. They have been married to my step parent for a long time and I consider them a parent also. I know if I were in step parents shoes I would want to know but they are in their 70's and health deteriorating (though nothing serious/imminent) I feel sick at the thought of destroying their marriage/our family but also don't feel right keeping it secret. Feel like I want to confide in my sibling and discuss how to approach but not sure if I should lumber him with it too.
Any suggestions how to approach it. Confront parent/tell step parent/ ultimatum?