The duo played together during their time at Arsenal and Song says the Spaniard is his 'brother from another mother.'
And, despite the fact that they will clash at Stamford Bridge later today, the West Ham man admits he is very happy for the Chelsea midfielder, who is enjoying plenty of success in the Premier League.
“Cesc is my brother from another mother. A good guy and a good player. I’ve known him since I was 17 when I signed for Arsenal. We grew up together. Then I moved to Barcelona," the West Ham midfielder told the Daily Mirror.
“On the first day that I arrived at Arsenal I slept at his house. I was supposed to go to a hotel but he said ‘no’. He told me to stay with him at his house. He gave me advice to help me get started and it is always a pleasure to see him.
“I’m so happy with the way Chelsea are playing with him in the team. It’s great because in his last year at Barca he didn’t get to play in every game."