Question: During the Ayodhya Yatra we heard that Vasistha destroyed all but one of the 100 sons of Visvamitra just by his mantra chanting (when Visvamitra had tried to drag Sabala away from Vasistha). Later it was mentioned that, for saving the life of Sunahsepa, Visvamitra requested his sons to sacrifice their life for Sunahsepa.
My question is:
Did Visvamitra have some more sons after those 99 sons got destroyed? The genealogical chart presenting the lineage of Visvamitra does not show that.
Answer by Romapada Swami: According to Valmiki Ramayana, Vasistha burned 99 of the 100 sons of Viswamitra by the power of his mantra.
Thereafter, Viswamitra performed tapasya and obtained weapons from Lord Siva. When Viswamitra could not overpower Vasistha even with the weapons given by Lord Siva, he began performing tapasya again in the southern region. He went to do tapasya along with his principal queen.
During the course of that tapasya, 4 sons were born: Havishpanda, Madhushpanda, Dridhanetra and Maharatha. These 4 sons are mentioned in the genealogical chart. After the birth of these sons, Viswamitra was bestowed the title of Rajarsi and thereafter the pastime of Trishanku and Sunahshepa took place.
The Valmiki Ramayana says that these (4) sons were cursed by Viswamitra when they refused to take the place of Sunahshepa
in the human sacrifice of Maharaja Ambarisa.
This addresses your question about the birth of the sons who were cursed, but not about the 100 sons. That answer is given in SB.
In the Srimad Bhagavatam too, the history of Viswamitra and Sunahshepa is given, but with several modifications.
SB says Vishwamitra had 101 sons. The death of 99 sons is not mentioned.
In SB, Vishwamitra does not ask his sons to take the place of Sunahshepa, but instead asks his 101 sons to accept Sunahshepa as their brother after the sacrifice. The 50 elder sons who refused to accept Sunahshepa as their elder brother were cursed while the remaining 51 received blessings from Vishwamitra for accepting Sunahshepa as their brother.
More details of the differences between the narration of Valmiki Ramayana and SB is given in the link. This was not included in the yatra lecture as it is too complex for a general audience to follow.