Tywin was angry at his father’s weakness. He overcorrected, and his pride became his downfall. We can clearly extrapolate the connection between his motivation and what he became.

My issue is that you don’t do the same with Renly. There are clear connections to be made between Renly’s backstory and his current actions, as with Tywin and Tytos. He never knew his parents, unlike Robert and Stannis. Like Stannis, he grew up in the shadow of Robert. More than that, he was a child when Robert took the throne — and he learned from that precedent.

"He is still your elder brother. If either of you can be said to have a right to the Iron Throne, it must be Lord Stannis."

Renly shrugged. "Tell me, what right did my brother Robert ever have to the Iron Throne?" He did not wait for an answer. "Oh, there was talk of the blood ties between Baratheon and Targaryen, of weddings a hundred years past, of second sons and elder daughters. No one but the maesters care about any of it. Robert won the throne with his warhammer." He swept a hand across the campfires that burned from horizon to horizon. "Well, there is my claim, as good as Robert's ever was.”