Merging Two Unrelated Sites into a Third Site

[OPM]

We have a new client interested in possibly merging 2 sites into one under the brand of a new parent company. Here's a breakdown of the scenario.....

BrandA.com sells a variety of B2B widget-services via their online store.

BrandB.com sells a variety of B2B thing-a-majig products and services (some of them large in size) not sold through an online store. These are sold more consultatively via a sales team.

The new parent company, BrandA-B.com is considering combining the two sites under the new brand parent company domain.

The Widget-services and Thing-A-Majigs have very little similarity or purchase crossover; so just because you're interested in one doesn't make you a good candidate for the other.

We feel pretty confident that we can round-up all the necessary pages and inbound links to do proper transitioning to a new, separate third domain though we're not in agreement that this is the best course of action. Currently the individual brand sites are fairly well known in their industry and each ranks fairly well for a variety of important terms though there is room for improvement and each site has good links with the exception of the new site which has considerably fewer.

BrandA.com DA = 73 - 19 years old
BrandB.com DA = 55 - 18 years old
BrandA-B.com DA = 40 - 1 year old

Our SEO team members have opinions on what the potential outcome(s) of this would be but are wondering what the community here thinks. Will the combining of the sites cause a dilution of the topics of the two sites and hurt rankings? Will the combining of the domain authority help one set part of the business but hurt the other? What do you think? What would you do?

[HiveDigitalInc]

If marketing/branding feels like they want all of them to be consolidated under the brand, I would go ahead and move forward, and just be sure to cover my typical site merger bases.

From my experience, it ends up happening at some point, so you might as well take advantage of the extra press, etc. that is likely happening from the merger to get it right as soon as possible.

[OPM]

But if you had a choice to merge or not merge the sites as we have outlined here would you or wouldn't you?

[HiveDigitalInc]

This is a common challenge for business during/after M&As...  Especially when the acquisition is to bring on a new service/product that was previously not provided.    A lot will hinge on the structure of the new site, and if it creates a clear user (and crawler) experience for these two separate facets of the new business.

I'm assuming you plan to create a homepage generally addressing the services/products of the company and providing users with the choice of going from the homepage to /brandatheme/  or /brandbtheme/ ... so you clearly differentiate the topics in the site structure, and can maintain the authority to their respective sections of the new site?

A consideration could be made to build the new site first, selectively canonical pages of the old sites for a transition period, and then doing the final redirecting... just so the change can be monitored.

I typically set an expectation to of potential short term losses, but net neutral over 6 months if the migration is done well.