The relative called dependable may be carrying a family habit of asking them first.

Being known as the reliable one is rarely a single decision. It builds from a hundred small moments where someone was easiest to ask, and after a while the asking stops being a choice at all. The label sounds like praise, though it also describes a pattern that keeps landing in the same place. What looks like a personality is often a habit the rest of the family has stopped noticing.

If you are the one always asked, you can say so plainly without accusing anyone. If you are the one asking, try starting somewhere else with the next thing that comes up.