The Altman Brothers

The Altman Brothers

The Altman brothers — Sam, Jack, and Max — operate several intertwined investment vehicles from San Francisco, deploying capital generated primarily from Sam Altman's tenure as CEO of OpenAI and former president of Y Combinator. Their investment footprint stretches across Hydrazine Capital, the family's primary venture fund, Altman Capital, and Apollo Projects, a vehicle focused on deep-tech and moonshot companies. The family office structure is unusually distributed across the three siblings, each bringing distinct operational and investment experience: Sam as the architect of the AI era's most valuable private company, Jack as the founder and former CEO of HR platform Lattice, and Max as a former partner at Apollo Projects. Their strategy skews heavily toward early-stage and high-conviction concentrated bets in technology. The portfolio is dominated by AI and enterprise software, but branches into climate tech, life sciences, and hard infrastructure. Confirmed portfolio companies include Helion Energy, a nuclear fusion startup where Sam Altman has invested $375 million personally (per TechCrunch, 2021); Retro Biosciences, a cellular reprogramming longevity company seeded with $180 million (per MIT Technology Review, 2023); and Humane, the wearable AI hardware startup founded by ex-Apple designers. The firm also holds significant equity in Reddit, Asana, and Instacart — all Y Combinator alumni from Sam's tenure. Geographic focus is heavily concentrated in the San Francisco Bay Area, with select bets in the Pacific Northwest and Europe. While no precise AUM is disclosed, filings and press reports suggest Hydrazine Capital alone manages well over $1 billion, with Apollo Projects targeting $1 billion in committed capital. The team remains lean — fewer than a dozen known investment professionals — leveraging Sam Altman's personal network and reputation to source deals. Jack Altman co-founded Altman Capital to manage a portion of the family's liquid assets and angel investments. The family maintains close ties to the Y Combinator ecosystem; Sam was president of YC from 2014 to 2019, and many of their largest public and private holdings trace to that community. Jack Altman stepped back from day-to-day operations at Lattice in 2023 to focus on Altman Capital. Structurally, this is a principal-led family office embedded directly in the fabric of the AI industry's most critical institution. Sam Altman's dual role as CEO of OpenAI creates a sourcing and diligence advantage that no competing venture firm can replicate — deal flow flows directly to him. This concentration of influence, combined with the brothers' split across pure venture (Hydrazine) and science-heavy project finance (Apollo), creates an entity that operates more like a distributed R&D lab than a traditional family office. The governance is informal but weighted toward Sam, with the brothers serving as a de facto investment committee for the largest commitments.