I very, very much doubt Apple will intercede in this. Your easiest route is to negotiate this with him. While you could create a new account, you may find it difficult to remove the old account from any devices you own unless you have the receipt for the purchase of your devices and can ask Apple to reset them entirely. In addition it would mean abandoning everything you ever did with the old account.
Apple can completely reset a device if a person can provide sufficient evidence of valid ownership. Read the requirements and steps for an Activation Lock support request at: https://al-support.apple.com/#/additional-support and links at the bottom right for the type of service requested. Apple says they may require "proof of purchase documentation” and that you need “proof of ownership documentation”, but does not detail what currently constitutes proof other than it “must include the product serial number, IMEI or MEID.” User reports on this community indicate that typically Apple will ONLY accept an original receipt issued by Apple or an Apple Authorized Reseller. Presumably this is the only kind Apple can authenticate against fraud since Apple is not involved in third party sales. Apple recommends that you "Keep your receipt after you buy an Apple device" --> Keep your receipt after you buy an Apple device - Apple Support