Gohan is 7 when Trunks first appears in DBZ.
Saiyan Saga: 4 Cell/Android Saga: about 11 Majin Buu Saga: 17 End of Dragonball Z: 26 Dragonball GT: 36
he is around negative two years old
I don't know but maybe someone will post in and answer. ( I THINK it MAY be sixteen)
Gohan had to save Trunks, who had been knocked out by Android 18. When he tried to hide, 17 and 18 blew up the whole area and flew away. When the smoke cleared, Gohan only had one arm.