I've used sitepoint for a lot of resources over the years but I'm finding myself dealing with a situation and hoping the experienced members might have some thoughts. I've considered looking up a lawyer but my area isn't known for a lot of computer/web technical legal expertise (farm region in the USA); though maybe the business aspects would be enough on their own.

I have done a bit of consulting and development work from time to time over the last 5+ years, things like updating a theme on wordpress, church websites, etc and have been working on focusing my efforts toward actual web applications - both custom requests and producing products for sale/subscription. I now find myself seeing some growth in three different areas:

1. A partnership I formed with some classmates working on a specific application with the potential for stretching into additional projects. This is mostly development with an eye to sell licensing or subscriptions.

2. A former sole proprietorship which has started to move into a quasi-official contract or employee hire (mostly family) but gaining ground to be run more than a name for personal projects. This is mostly a case of some family members breaking into web consulting as well and us deciding to leverage our efforts rather than split the load and skills.

3. That same sole proprietorship still has a name and/or my personal name as the go-to for random projects from the community.

The family relationship isn't an issue, we've done other business type work so I'm not concerned about some of the standard family-related stresses in business. I am working on aligning my personal project efforts (#3) in with the group effort (#2) to create a more coherent presence.

The issue is both the partnership and the sole proprietorship will have an aspect of custom application or site design (not just throwing wordpress themes up) for specific requests as well as developing applications (browser or smartphone).

In both cases I'm the primary developer. The partnership is structured equally between three developers (including me). Certain areas of the partnership code are entirely mine whereas other areas are mostly mine and then there's areas which are slightly to speak. Some of the same conventions and structures I've polished in the partnership code lend themselves attractively to some of the sole proprietorship/family projects.

So the question:
What would be some recommendations to do or consider in maintaining the code base and intellectual property?

Since I don't consider myself "expert", I don't feel I'm up for completely re-writing functional code (for example a debugging class) "just because". I don't know if it's ok to mix the code as long as I don't claim my partner's code as my own. Is it ok for me to include my sole proprietor code into the partnership code since I'm the 'owner'? Should I be more official and "license" the code in one direction or another? How does that work when there is not really any money involved (no finished product yet)?

I also work as a developer for another company (contract work) but the circumstances are such it's very easy for me to keep the code bases and time spent separate from the other described projects. But the experience there has me mindful of the whole "code done for the boss is the boss' code". Easy to keep straight when I'm the employee...but how do I handle it when I'm the boss and the code is not a specific clients (like a for-scratch website of a local business).

To me the obvious and cleanest solution is to fold both business ventures together somehow. But I'm not sure how, and there's the issue of me giving up control over what is sort of a family business versus "weakening" my partners' influence in the partnership, depending on which venture folds into the other. The trickiness there has me hoping I can find a more code or license oriented solution than a business structure solution.

Any suggestions?