I'm just curious: please explain how the addresses are mathematically related.
Since if those are the common P2PKH addresses, those are just encoded "HASH160" of the public key.

BTW, there a lot of old and new topics here that discussed unrelated transactions with matching R value.
Most of the legit ones are implementation bugs from old wallets or old versions of wallet that are still available today.
Check the advanced Forum Search function (/index.php?action=search) to check if the related addresses have been discussed on any old topic.