I have been told that Aragorn was taken and raised amongst the Elves in one of my previous questions.
Was there anyone who was aware of this? If so since he is the heir of Isildur did anyone search for him?
When people were aware of him and his legacy, were there any human supporters who agreed to his right to get the throne and willing to fight for him?
The people of the Dunedain were indeed aware of his fostering in Rivendell as it was tradition for their Chieftains to be fostered there (Elrond did not take Aragorn but provided the traditional service of raising the future Cheiftain, having been aware of their lineage stretching back to his own brother, Elros), where the heirlooms of Isildur were kept:
Arahael his son was fostered in Rivendell, and so were all the sons of the chieftains after him; and there also were kept the heirlooms of their house: the ring of Barahir, the shards of Narsil, the star of Elendil, and the sceptre of Annúminas.
The Return of the King - Book 7, Appendix A: (iii) Eriador, Arnor, and the Heirs of Isildur
The Gondorians however, were unaware of the happenings in the North, and as far as the books lead us to believe were unaware of the Heirs of Isildur still existing. (As covered in this Q&A)
Had Aragorn chosen to announce his kingship after coming of age, he would've had support from the Dunedain as he was the Chieftain of that people. However, as covered in this Q&A, an earlier return by Aragorn would've led to the rejection from the people of Gondor, the largest population of Men and the most powerful, and as such he would've been cast aside, as Arvedui had been before him.
Elrond had long been a friend to the Dúnedain of Arnor who became the Rangers. Their chiefs were direct descendants of Isildur. Aragorn's father, Arathorn, was killed fighting orcs when Aragorn was just two years old. In order to safeguard the line of Isildur, Elrond offered sanctuary to the infant Aragorn and his mother Gilraen. He was given a fake name (Estel) and not informed of his true identity until he came of age.
We can speculate that the most senior Rangers would have probably known what had happened to their future chief but they would have dissuaded anyone seeking him or even discussing his whereabouts.
