Basically, the writers always envisioned Riker and Troi would marry at the end of the series, but Rick Berman overrode them and forced the Worf romance because he wanted to mix things up.
Marina Sirtis and Jonathan Frakes both hated the Worf romance because they felt their characters were basically destined to end up together from the very beginning.
It was never actually explained canonically, but basically everyone hated it except Rick Berman and Michael Dorn and if they married Deanna and Worf in Generations Nemesis (mixed up which movie they got married in), I guarantee it would’ve led to a lot of very angry fans.
https://screenrant.com/star-trek-next-generation-worf-troi-couple-dating-bad/
I don’t know about firstest, but he was definitely firster. That’s why they call him a founding father, not a founding fathest.