Tina Knowles' New Hubby -- So Tight With Beyonce & Jay Z ... He's Already Plugging 'Em

Tina Knowles' hubby, Richard Lawson, is all about his new stepkids Beyonce and Jay Z -- and to prove his loyalty he put in some work for one of their flailing business ventures.

TMZ broke the story ... Richard and Tina tied the knot a couple weeks ago -- and Wednesday in L.A. he said their families are totally bonding already ... partly, he says because he and Tina have been tight for decades.

But you gotta see papa-in-law go into pitch mode when the photog brings up Tidal -- Jay Z's music streaming service. Sales of the app have plummeted, but you'd never know it from Richard's enthusiasm.