A Robert Greene power-law paired with Despise the Free Lunch (Law 40): when asking a powerful person for help, invoking past favors or a sense of owed gratitude ("I helped you before, my brother worked for you") is the single worst approach. Nobody wants to feel like they owe someone — gratitude is an unreliable currency, and reminding a powerful person of a debt tends to trigger resentment rather than repayment.
The working alternative is research, not reminders: find out what the specific powerful person needs, lacks, or has been unable to get, and package the ask around delivering that. Time and attention are named as the scarcest resource almost every powerful person shares, so proposals that visibly save them time or reduce exhaustion carry outsized persuasive weight — because they serve the target's self-interest today, not a debt from the past.