The court heard that the attack had its roots in a feud between the TN1 (Trust No-One) gang from the Tulse Hill area of south London and Brixton-based GAS (Guns and Shanks).
Idiabeta and Okusanya were members of the TN1 group out to avenge one of their number who had been stabbed in a bus garage attack carried out by the GAS gang earlier in the day.
Kwame's father Kwaku, a sports journalist, told the court in a statement that his son was full of potential.
He was in the sixth form of Forest Hill School and excelled in sport, music and acting and was ambitious.
Mr Ofosu-Asare said: "Kwame was a very vibrant, energetic and enthusiastic boy.
"His brother and sister are struggling to cope with his death. All our lives have been ruined."
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Delays, diversions and cancellations caused chaos to services on South West Trains which were hit by signal failures in south west London.
During the attack Ione Wells' head was smashed against the pavement, her attacked grabbed at her chest with such force that it tore her bra.
The 17-year-old pushed her to the ground and smashed her head against the pavement, before grabbing at her chest.