Choosing display names for others rather than oneself

Current state of things: Contacts are listed under the display name they have chosen (or if they didn't, their username or even their ID)

Suggested change: Instead, I think it would be better if users could choose the display names for their contacts, similarly to what people do when adding phone contacts (also, syncing those names with their linked devices would be a real plus)

Why this would be better: There are various cases in which a user would want to appear with a different name to their various contacts. Here are two which directly concern me:

• I'd like using my full name for my colleagues, and my nickname for my friends
• Maybe more relatable: I'd like my parents to appear as "Mom" and "Dad" (which aren't the display names they are going to choose for themselves if they have other contacts)