We propose a dual primordial black hole (PBH) formation scenario realized in two-stage inflation separated by a noninflationary break. A single comoving scale re-enters the horizon twice, leading to the formation of two PBH populations at different epochs: ultralight PBHs during the break stage and heavier PBHs after inflation. The former evaporate before big bang nucleosynthesis and can reheat the Universe, while the latter may account for all dark matter today. We show that the required hierarchy in PBH abundances arises naturally from the suppression of curvature perturbations during the break. This scenario predicts a distinctive bipeak stochastic gravitational wave signal, originating from PBH evaporation and enhanced curvature perturbations, which lies within the sensitivity of future observatories such as LISA and DECIGO.

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• Gravitational wave sources
• Gravitational waves
• Inflation