The short answer is, yes it can be. An informal relationship may give rise to a fiduciary duty when one person trust in and and relies on another, whether the relationship is a moral, social, domestic, or purely personal one. A fiduciary duty based on an informal relationship may arise when a high degree of trust, influence, or confidence has been acquired and abused. A fiduciary relationship may also arise either as a result of dominance on the part of one or weakness and dependence on the part of another.
Pearls of wisdom: Just because you don’t have a formal fiduciary relationship with another doesn’t mean that you don’t owe that person a fiduciary duty.