Associated employments - NIC

I have a client who has two jobs with the same person. However, one employment is with his company and the other is running his personal lettings business, which is assessed under the employer as an individual and not through a company. The lettings are not connected with the company in any way.

I know if the employment was for two companies and the employer had control etc, they would be related, but what about a company and an individual? The employer is the sole director/shareholder of his company.

Thank you, in advance.