This is called chart rectification (定时辰) and it's an advanced practitioner skill. Methods include:
1. Life event mapping. Major life events (marriage years, career changes, health crises) are matched to likely Luck Cycle and annual triggers. If you married in a year when Spouse Stars are prominent, those years help narrow the hour.
2. Personality profiling. Hour Pillars influence inner character. A person with a Tiger Hour is bold and initiating; a Goat Hour is gentle and peace-seeking. Your known personality can hint at the hour.
3. Physical traits. Some traditions associate Hour Branches with physical characteristics.
4. Relationship with children. The Hour Pillar represents children. If you have clear information about your children's temperaments or your experience of parenthood, it offers clues.
This process requires a skilled consultant and ideally multiple reference points. It's not perfect, but it can narrow the birth time to the correct double-hour.