My company needs help evolving our messaging from one to multiple related products due to acquisitions. How do you align people to think beyond the product they started with?
Going from single to multi product is a great challenge to have!
Rather than ask how you can align people internally, I'd challenge you to take the outside in view first: why would your customers care? Which personas of yours fit with each offering (primary, secondary) and what are the problems they are looking to solve?
Once you have created a map between your product lines and your personas, you can think about putting a wrapper around the combined solutions for each audience:
What is the 'better together' story between all your offerings?
What do you even call that combined offering?
What assets does your sales need to explain that combined value?
Rather than just a list of product offerings, it's your job as a PMM to find or create the red thread that links them together for your audience. Don't underestimate the power of storytelling - for either an internal or external audience.
Put the product aside and think about your audience (whether they're buyers or end users). What are their JTBD? What are the major challenges they're facing?
Then, examine the products you have at hand. What are the various use cases they unlock? Think of the products and features as ingredients - and the value you're trying to show case to your audience as meals. You're trying to come up with a dinner plan. You wouldn't create an entire meal with just one type of ingredient (let's say broccoli). And what kind of meal are you trying to create in the first place - a soup? A roast?
Once you get your head out of just thinking about your product, and just focus on your audience's challenges, needs, wants, JTBD, you'll be glad to have more than on product to work with.
Structurally, what I have found also helps is having folks in-seat whose remit is to work across the portfolio - to build messaging across a number of products. A PMM dedicated to product X is just going to think about X, even if they try not to. But having a few PMMs dedicated to marketing overall innovation or across a number of products is ensuring that your organizational structure supports your messaging goal.