Thank you for posting--it seems this ties quite well with the discussions on establishing appropriate boundaries between child and parent. Word incest implies something physical but it is not the case with these type of relationships--which imply inappropriate emotional attachments--where as the adult expects the child to satisfy emotional needs and roles. It is role reversal the child is satisfying the emotional needs of the adult when more appropriately the adult should be satisfying the emotional needs of the child. The extent can be minor to excessive. The child is brought into adult life as a confident to adult issues and problems--which should never have been shared with the child.
I am sorry you have experienced this type of behavior and I like many have seen the effects of "unboundaried bonding". So it is not solely narcissists who have this type of behavior.