(Bloomberg) -- When Saudi Arabia announced last week a $20-billion investment in a U.S. infrastructure fund managed by Blackstone, many noticed that it came shortly after presidential son-in-law Jared Kushner personally negotiated a $110-billion arms sale to the country. What went unnoticed — and is largely unknown — is how important Blackstone is to the Kushner family company.

Since 2013, Blackstone has loaned more than $400 million to finance four Kushner Cos. deals — two of which have not been reported — making it one of the business's largest lenders. And their ties go beyond the loans. Stephen Schwarzman, Blackstone's co-founder and CEO, heads Trump's business-advisory council and was in Riyadh with the president and Kushner. The Saudi promise to invest in Blackstone's fund drove the firm's stock up more than 8%.

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