Specifically in relation to Satine Kryz's New Mandalorians, Jaster Mereel's True Mandalorians and Tor Vizsla's Death Watch?
The Clone Wars wiki seems to imply that the TV series has combined Satine Kryz's pacifist New Mandalorians with Jaster Mereel's honorable mercs, the True Mandalorians and implies Satine as Jaster's political successor.
The New Mandalorians were a large group of Mandalorians led by Duchess Satine Kryze and before that Jaster Mereel, who were pacifists. The Death Watch despised them and wanted to "liberate" Mandalore from them on numerous occasions.
By the time of the Clone Wars Era, the Mandalorians had renounced the violence and desire for conquest which haunted most of their history. Under the leadership of Jester Mereel who authored the Supercommando Codex the people of Mandalore became friends of the Republic. However not all Mandalorians stood with Mereel and his attempt to civilize a savage society and so a splinter faction known as the Death Watch was formed.
In older EU, according to Wookieepedia, however, Jaster's political successor is Jango Fett, though all of his faction wiped out by the Jedi thanks to a dirty trick by the Death Watch
Jango Fett succeeded [Jaster Mereel] as the new Mand'alor and leader of the True Mandalorians until the devastating defeat at the Battle of Galidraan against the Jedi Order. There, a Death Watch scheme unfolded that brought a contingent of Jedi Knights led by Master Dooku to the planet under the false pretenses that the True Mandalorians were murdering civilians. When the Jedi attempted to take them into custody, fighting broke out that left eleven Jedi and every True Mandalorian on Galidraan dead, save for Jango Fett.
After being imprisoned by Jedi, Fett was responsible for destroying the Death Watch, a Mandalorian group who killed Fett's mentor, Jaster Mereel.
As such, according to the latest canon on Mandalorian history as provided by only the Clone Wars TV series (or other canon of the same level) is Jango Fett still the adopted son/protégé of Jaster Mereel?
Edited in 2021: I'm curious how things have changed with whatever's the latest in the post-Disney world of Star Wars, what with more Mandalorian lore coming in from "The Mandalorian", and earlier stuff like Rebels, post-Clone Wars.