Board Thread:Lore Discussion/@comment-5632187-20130203042433/@comment-122.59.106.72-20130503211249

speculation:

Gwyn's firstborn was stripped of his status after Gwyn went to the kiln of the first flame we know this because he left his miricle on the tomb of Gwyn "When the eldest son was stripped of his deific status, he left this on his father's coffin, perhaps as a final farewell." therefore for Gwyn to have a tomb he must be dead

I think the firstborn is still alive as on the sunlight medal it says "But the old God of War still watches closely over his warriors."