Distance and Age Determination in NGC 7129: Gaia DR3 Astrometric Selection of a High-Confidence Member Population Reveals a Depth-Extended Association with Multiple Stellar Generations

We present a Gaia DR3 astrometric analysis of the young star-forming region NGC 7129, aimed at identifying a high-confidence member population for precise distance and age determination. Using two independent selection pipelines — an initial ranked astrometric scoring and a second-stage iterative proper-motion clipping on an expanded sample — we recover a robust distance of 920 ± 40 pc for the main component. The re-analysis resolves the member population into two kinematically coherent distance components: Component A: 904 ± 60 pc (101 stars) Component B: 1108 ± 35 pc (53 stars) These components show no projected spatial separation but are separated by ~200 pc along the line of sight. The proper-motion dispersion (~9–10 km/s) is inconsistent with gravitational binding, indicating a partially dispersed association rather than a bound cluster. Isochrone fitting with differential reddening, corroborated by the kinematic age indicator, places the optically revealed population at ≥5 Myr (consistent with 6–15 Myr), significantly older than the classical ~3 Myr estimate for the embedded component. A wide-field (2°) query confirms that this kinematic locus extends regionally (~500 ± 25 excess sources above field background) with azimuthally symmetric projected morphology (axial ratio a/b = 1.03), consistent with an end-on viewing geometry of a filamentary complex. The region hosts at least two star-formation episodes: the embedded 1.8–3 Myr component from the literature and an earlier optically revealed generation now dispersing. The derived distance resolves long-standing discrepancies in the literature (900 pc to 1.26 kpc) as successive samplings of different portions of a depth-extended structure.