A plausible theory I came up with...

I came up with what I think is a plausible theory regarding Muldoon and Roland.

The two of them are brothers. What makes me think this:

1. Both are experienced big game hunters.
2. Both dress virtually the same.
3. Both would be roughly the same age.
4. Both of them are British.
5. Both of them end up working for InGen.

The two men are brothers, and Roland heard off Muldoon that ingen have bred Tyrannosaurs, then became increasingly obsessed with the idea of taking one down for his ultimate trophy. I think he would have been jealous of Muldoon as well, with Roland thinking here I am hunting all the generic animals that everyone has hunted a million times before and here's my brother over there on that island with a T-Rex on his doorstep. He might have also become obsessed due to the fact Muldoon dies in the first film, so by taking down a male rex, it was also a way of avenging his brothers death. I think Roland probably got in contact with Peter Ludlow and asked if he could step into his brothers role working for InGen.

There's also a line in the original novel where Muldoon says (talking about the adult male rex), "I've been wanting to put a needle in this big bastard for a while now", Which is exactly what Roland ends up doing to the male rex in The Lost World.

Anyway, thought it was an interesting theory, let me know what you guys think.

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.)

That is an interesting theory! For some reason i never thought of it before.. Food for thought.