I agree with you, I don't really care how this is called... but when two parent do not fulfill their emotional needs in each other or in other adults and they come to their children for that - it can't be healthy. Children also feel special in this dynamic but it has consequences. Trust me, if you would like to resolve this kind of relationship, it would lead to nasty breakup between parent-child like between two romantic partners.
Its called something like "emotional parentification".