Originally posted by: NoraSM
@red
It is stated that Arjuna trained Abhimanyu and Upapandavas
'The child from his earliest years became the favourite of Vasudeva and of his father and uncles, like the moon of all the people of the world. Upon his birth, Krishna performed the usual rites of infancy. The child began to grow up like the Moon of the bright fortnight. That grinder of foes soon became conversant with the Vedas and acquired from his father the science of weapon both celestial and human, consisting of four branches and ten divisions.'
His father and Vasudeva are mentioned separately, the last sentence stays that his father trained him
'All of them, of excellent behaviour and vows, after having studied the Vedas, acquired from Arjuna a knowledge of all the weapons, celestial and human'
This one States Arjuna trained Upapandavas too
https://www.sacred-texts.com/hin/m01/m01224.htm
@Blue
Ghatothkach's son and Bheema's grandson also participated in war
Afflicted with showers of shafts by Bhimasena's grandson, viz., the brave Anjanaparvan, Aswatthaman looked like the mountain Meru bearing a torrent of rain from a mighty cloud.
https://www.sacred-texts.com/hin/m07/m07152.htm
Ghatothkach growing up + having a grown up son who can participate in war, is not possible if Abhimanyu and Upapandavas were teenagers
@green -/Abhimanyu's birth is described before Khandaprasth Dahan incident where Arjun got Gandiva, Dhrithrashtra clearly states that 33 years have been passed since the burning of Khandavprastha
"Three and thirty years have passed away since the time, when Arjuna, having invited Agni, gratified him at Khandava, vanquishing all the celestials. "
In all this, Upapandavas and Abhimanyu participated along with their uncles in Rajysuya Yagya
"O king, followed Suvala with his son; and the sons of Draupadi with the son of Subhadra followed those mighty warriors--the kings of the mountainous countries. And other bulls among Kshatriyas followed other Kshatriyas. And the Brahmanas by thousands also went away, duly worshipped.
https://www.sacred-texts.com/hin/m02/m02044.htmsons
They were old enough during this yagya to follow kings themselves
After reading all this, I came to a conclusion that Abhi was 30+ and Arjuna was very much a part of his childhood and Early training, but again, it depends on what one believes as there are many contradictions in the story
@purple
Like Kunti was mother figure for Nakul and Sahdev but they are called Madri's sons