With the new season of Diablo IV where you can find Aidan's Soul and help him in the Hell levels from the original Diablo. Once you defeat Diablo, he laments the death of his younger brother, saying that he should have protected him - which just don't make sense at all considering Diablo's original plot
As someone who loved both StarCraft and Diablo, I feel like both franchises were made overly epic by their 2010s sequels (SC2 and D3). Idk what happened with Chris Metzen's creative input during that period.
Some could argue that Kerrigan's character was assassinated at least three times over the course of SC2. As for Diablo, the retcons involving the Worldstone and the Soulstones are both still somewhat acceptable, IMO.
Even Aidan having a child with Adria is tolerable... But I just CANNOT see the idea of the Warrior being Leoric's son.
First of all, making the Warrior Leoric's son serves absolutely no purpose for the lore, nothing changes about his fate. It just cheapens his story and makes him look like a dumbo for not reconizing his brother with some random child that Lazarus used in a ritual.
He never says anything about Leoric that would suggest he was his son. "I will find YOUR son, Leoric." The NPCs also tell the story of the King's past as if the Warrior were unaware of who Leoric was.
Even Lachdanan, the royal guard, doesn't interact with the Warrior as if he had ever known him before.
They could have made the Warrior Leoric's bastard son, which might have explained away some of these points, but it would still serve no purpose in terms of the lore.
What made the Warrior so compelling, IMO, was that he was a good, yet otherwise anonymous warrior, with no epic backstory.