Possibly
Person Y is possibly in a fiduciary relationship with Person X. Person Y is acting as an agent and possibly a broker for Person Y - both of these positions create a fiduciary relationship.
A fiduciary is someone who has undertaken to act for and on behalf of another in a particular matter in circumstances which give rise to a relationship of trust and confidence.
— Lord Millett, Bristol and West Building Society v Mothew
The fiduciary's duty is to act in the other person's best interests. That does not necessarily mean following the other person's instructions, but if they don't, they should have a very good reason for why they didn't.