iCloud+ custom email domain with different iCloud mailboxes

Currently I use iCloud+ custom email domain for my personal email, say me@personal-domain.com. I remember reading somewhere that, while you can add extra domains and aliases, they all forward to the same iCloud account. You can sort them to different mailboxes using rules, but ultimately, all mails are stored under a single account. Now a situation has come up: my wife and her business partner have a small business for which they have registered a custom domain, used only for emails (no web page hosting). There are two email accounts, say wife@business-domain.com and partner@business-domain.com, and no expectation of needing more accounts in the future. Initially they were set up with a DreamHost introductory offer for 3 years, but it's expiring this month, and the renewal price is way higher than that introductory offer, so we're looking to move it somewhere else cheaper. Ideally, we would like to have three iCloud accounts (one for me, one for my wife and one for her business partner), so we could forward me@personal-domain.com to my iCloud account, wife@business-domain.com to my wife's iCloud account, and partner@business-domain.com to the business partner's iCloud account. I'm not comfortable with e.g. her business partner being able to peruse through my personal emails -- in that case we would rather pay for a separate service for their business domain. Question: is it possible to somehow forward these three separate emails (one on my personal domain, two on the business domain) to three separate iCloud accounts? Perhaps using Family Sharing?