The original Captain Marvel is famous for being one of the few major superheroes to die and stay dead. Except actually, Mar-Vell has been resurrected as part of both the Secret Avengers and the Dead Avengers and then quickly died again in the same story like a dirty cheater. His son though, has actually managed to stay dead.
Genis-Vell was created from the original Captain Marvel's DNA by his lover Elysius. Just like his father, Genis wound up bonded to the human Rick Jones and so took up the mantle of Captain Marvel (much to the annoyance of Monica Rambeau, who was using the name at the time).
Initially the two hated each other, but Genis and Rick were eventually able to overcome their differences and became friends. Eventually, Genis was seperated from Rick and struck out to become a hero on his own, taking the name Photon (much to the annoyance of Monica Rambeau, who was using the name at the time).
After a confrontation with the Thunderbolts, Photon ended up absorbing two alien gems known as the moonstones, boosting his powers. However, his new powers threatened to tear apart the entire universe and so Baron Zemo had no choice but to, not just kill him, but to scatter his remains across multiple dimensions so that they could never be reuinted.