You should probably include the correction Shane made later:

https://twitter.com/shane_riordan/status/1354787975058616320

"Citadel isn’t a majority owner of RH, but they DO pay RH a hefty figure to the app for consumer data. On top of the money paid to bail out Melvin.

All they have to do is threaten to pull that money for data from RH and RH pulls new share purchases of $GME.

It’s wild."

Citadel doesn't own Robinhood.

Yeah, I keep seeing this claim posted that Citadel owns Robinhood, but I can't find any evidence to back it up. The Wikipedia pages for each don't mention the other.