There's a lot of holes in that theory....tbh. (And none of your points (other than the fact they are both British-descended Kenyans) really shows that they could be related.
They have different surnames. Muldoon (along with all of InGen's employees) were bound by NDAs.
And Muldoon is way too much of a professional to be breaking an NDA. (Though I wonder how much the Costa Rican, Dominican, and American governments knew about the Jurassic Park project.)
The way Roland had asked Ajay about the "expedition", it's obvious Roland had no knowledge that dinosaurs had been recreated. (Though this is a deleted scene, and their canonicity is kinda debatable (rule of thumb usually dictates that unless considered otherwise, deleted scenes aren't usually canon.)
But taking the scene into account, Roland's quest to hunt a Tyrannosaur would basically give him bragging rights as being the only human in the world to have hunted a Tyrannosaur, and would be the envy of other big-game hunters. I think that Ajay's death was a sobering moment for Roland, and his line "I think I've spent enough time in the company of death" alludes that he is retiring as a hunter.
Also, why would Roland tranquilizing a Tyrannosaur avenge Muldoon's death, when Muldoon was killed by Velociraptors? (Roland would had to have killed The Big One, which we already know was lunch for Rexy.)