I would not depend on facts from a housemate.
Concerning Ho Chi Minh, he was not of Royal Blood and he could not establish a Royal Dynasty.
Ho Chi Minh did however by force establish a Communist Regime in North Vietnam, that in time invaded South Vietnam and united the country under Communism.
Concernig the history of the Nguyen Dynasty and succession of dynasties information can be obtained here:
http://users.panola.com/vietnam/crown.html
When prior dynasties were established, I didn't think that they were always established by persons of Royal Blood. For example, one history says --
"The Later Le Dynasty (1428-1527)
From 1418-1428, LeLoi from a prosperous peasant family led a successful revolt against the Ming gaining independence back. In 1428, LeLoi ascended the throne beginning the Later Le Dynasty.
The Later Le ruled the country until 1527 when overthrown by MacDangDung."