Conversation so far:
How were the Sinhalese kingdoms formed?
Tambapanni.
Who or what are the Tambapanni?
landed on the island at a site believed to be in the district of Chilaw, near modern-day Mannar, and founded the Kingdom of Tambapanni.
Is this were the Sinhalese live today?
after the death of Vijaya and the end of the Kingdom of Tambapanni.
Who is Vijaya?
Prince Vijaya and his 700 followers left Supparaka, landed on the island at a site.
Did he take over the Sinhalese people?
Tambapanni was originally inhabited and governed by Yakkhas, having their capital at Sirisavatthu.
Were the Sinhalese people always there?
landed on the island at a site believed to be in the district of Chilaw, near modern-day Mannar.
How well are the Sinhalese doing now?
Upatissa Nuwara was seven or eight miles further north of the Kingdom of Tambapanni.
Is there people thriving?
CANNOTANSWER.
Are there any other interesting aspects about this article?
At the end of his reign, Vijaya, having trouble choosing a successor.
Did he choose anyone?
invite his brother Sumitta to take over the throne.
However, Vijaya had died before the letter had reached.

Question: Did the brother take over anyway?
Self-contained rewrite: Did the Prince Vijaya's brother take over the throne anyway?