Jonathan is important to the plot of Scholarship, he was a close friend of Pip. However, in real life Jonathan did not exist, he is actually a composite of three boys.
Mostly Jonathan is R. R had a great nickname, he was one of a large number of brothers from a Catholic family, so shared some of the guilt that Catholicism seems to thrive on. That he trained to be a priest did not surprise me, nor that he decided that priesthood was not really for him, also did not surprise me. I see he now works abroad, no doubt supported by his faith.
Jonathan also has a chunk of S in him. S was up for anything. He was the naughtiest boy in the school but only because that is what people thought he was. He never did anything terrible, just a bit of a mischief but his name was often called out at assembly, and that meant big trouble for him. Even then, S was good looking with short very blonde hair and a permanent suntan. I saw him some years later, walking down the other side of the street. I wish I had plucked up the courage to speak to him, but he was with another boy from school, so I did not as they looked like they might be an item.
Jonathan also had a bit of C in him. C was another natural mischief, very high spirited and adventurous, often in trouble. His father was a famous expert and used to appear on TV ever so often. I thought C would go on to do something similar, but there is no sign of him since we went to different schools.