Once upon a time, Roro Anteng and Joko Seger lived on the foot of Mount Bromo. After six years of marriage, they had not had any children. They prayed, pleaded to Gods for children. Their prayer was granted in one condition. They should sacrifice their youngest son to the Bromo crater. After sometime, Roro Anteng gave birth to a child, and it happened every year until they had 25 children. They lived happily and forgot about the agreement. The mount Bromo erupted signaling that the Gods asked the couple to fulfill their promise. But they didn't want their youngest son. Raden Kusuma, to be sacrificed to the crater. Raden Kusuma learned about the deal his parents had made. Meanwhile the lava from the crater had made the people living near the mountain suffered. Since Raden Kusuma was a kind and noble man, he didn't want his siblings and other people suffered because of him. Therefore he went to Mount Bromo and sacrificed himself to the crater. The eruption suddenly stopped. After that day, the Tengger people have given offerings to the crater, as Raden Kusuma had sacrificed himself before. Why did Roro Anteng and Joko Seger have to sacrifice their youngest son?

Question

Once upon a time, Roro Anteng and Joko Seger lived on the foot of Mount Bromo. After six years of marriage, they had not had any children. They prayed, pleaded to Gods for children. Their prayer was granted in one condition. They should sacrifice their youngest son to the Bromo crater.

After sometime, Roro Anteng gave birth to a child, and it happened every year until they had 25 children. They lived happily and forgot about the agreement. The mount Bromo erupted signaling that the Gods asked the couple to fulfill their promise. But they didn't want their youngest son. Raden Kusuma, to be sacrificed to the crater.

Raden Kusuma learned about the deal his parents had made. Meanwhile the lava from the crater had made the people living near the mountain suffered. Since Raden Kusuma was a kind and noble man, he didn't want his siblings and other people suffered because of him. Therefore he went to Mount Bromo and sacrificed himself to the crater. The eruption suddenly stopped.

After that day, the Tengger people have given offerings to the crater, as Raden Kusuma had sacrificed himself before.

Why did Roro Anteng and Joko Seger have to sacrifice their youngest son?