A version of this article first appeared in CNBC's Inside Wealth newsletter with Robert Frank, a weekly guide to the high-net-worth investor and consumer. Sign up to receive future editions, straight to your inbox.

Deal-making may have rebounded on Wall Street , but investment firms of the ultra-wealthy are still moving cautiously. Family offices made 54 direct investments in September, down 46% on an annual basis, according to data provided exclusively to CNBC by private wealth platform Fintrx.

Despite the broader slowdown, billionaire family offices are still investing in mega-rounds for high-flying startups. Last month, the firms of Amazon founder Jeff Bezos and former Google CEO Eric Schmidt joined a $300 million seed round for Periodic Labs. Founded b

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