Start with the part that is verifiable
Separate the event you can describe from the motive or reaction you are guessing. For a message about how to apologize after a holiday family argument, use this factual base: describe what you did, the family context it affected, and any responsibility that still needs attention.
Make one answerable request
Give the recipient one concrete question or next step instead of several emotional jobs at once. Make a direct repair to the affected person and change the practical pattern that caused the problem. Make the immediate next step clear enough that the recipient can answer without reconstructing the entire history.
Leave the recipient in control
Do not invoke family loyalty, childhood history, or a holiday deadline to force reconciliation. Keep children and vulnerable relatives out of adult conflict and follow any safeguarding or court requirements. A clear message remains useful even when the answer is no or no answer arrives.