If a business owner is a silent partner, and not an employee, they do not need to be included in the SEP IRA. You have to offer SEP IRAs to all of your employees.
If the business owners are not employees of the business, you do not need to offer a SEP IRA to them. If you intend to include one partner but not another, you should take care to ensure that whatever criteria you used to define who is eligible in your plan document will hold up to scrutiny.
A partnership deducts contributions to employee SEPs are a business expense, and their own contributions pass through to be deducted on their personal 1040. An IRS publication from several years ago made it clear that individual partners cannot have their own separate SEP accounts, since it must consider all of the employees of a business.