How do you market coaching when there are two coaches?

My sister and I are delving into coaching. I am in the process of getting certified at LCS (certification in September!) and my sister is probably not going to be getting certified at this time (or maybe ever). We both independently decided that we wanted to pursue weight loss coaching. I am a dentist and my sister is a physician. After discussing our vision, we are seriously considering going into business together – I would be seeing clients to work with them on managing their mind and overcoming obstacles, etc, while my sister would actually be helping the clients by formulating medical weight loss plans (diet, exercise, etc). I am having general confusion as to how the structure should be set up. I also don’t know how two people market together. I know this is a very vague question, but I really am looking forward to guidance.

I also have a few questions pertaining to forming an LLC and having consent forms. Do you think these are necessary prior to starting with clients (both fee and paid).

Thanks in advance!