Justin,
I've published a parenting book with a major publisher on children's friendships, and I have another parenting book in the works. I'm a psychologist with a PhD, I frequently speak at conferences and schools about children's social and emotional development, and I've been quoted in magazines and newspapers through out the country.
I'm telling you all of this, not to brag, but to demonstrate that the market for relationship/self-help books is very, very tough: My new book has been turned down by several major publisher because they felt my platform was not big enough (although some other publishers are interested). So, yes, without a degree, an affiliation with a major university, your own syndicated column or national TV show, or some other means of connecting with a large audience, you'll have a hard time getting a major publishing house interested in your relationship book.
You have two main options to increase your odds of publishing your book: You could try to find a collaborator with credentials and a big platform, or you could target smaller publishers.
I think it will be very hard to find a collaborator. No ethical people are going to want to just put their name on your book, and true experts are going to have enough of their own ideas that they'll prefer to write their own books or at least work with a colleague they know well.
I think your best bet is to target smaller publishers, but you'll still have to establish your credibility somehow. Have you had interesting or unusual life experiences that lead to your insights? (It would be especially good if you have a dramatic story that would lend itself to media coverage.) Have you used your insights in some way to help others? Do you have some overlooked facts/data to back up your surprising assertions? Have you played a leadership role in some organization related to the difficulties you address? Do you have or could you build the go-to website that contains lots of facts/information about the difficulty you address?
A "sells itself" proposal is one that establishes that there's a lot of potential reader interest in your topic AND that you're the one to write this book.