I don't know if they ever merged, I don't think they did....something new for me to look up!
However!
While there were lots and lots of different manufacturers in the earlier days of sewing machines, there were only a few cabinet makers, and I don't think any of the companies made their own cabinets. I've seen similar cabinet irons, and cabinets themselves for Singer, National, Davis, White....with Singer being the most unique and possibly making their own....
YAY!! Something new to research!!