CAN AN ACCOUNT BE ASSOCIATED WITH A CUSTOM RELATED RECORD

CAN AN ACCOUNT BE ASSOCIATED WITH A CUSTOM RELATED RECORD

I have a custom module which i want to link it with Accounts or Contacts using API. However, dev docs stated that only some module relations are supported by update record API:

Campaigns - to - Leads, Contacts
Products - to - Leads, Accounts,
Contacts, Potentials, Price Books

Is there anyway i can achieve this using supplied APIs? Please help.