Tony never felt as though he had real friends aside from Rhodey, Happy and Pepper. Pepper eventually went on to become more and Tony was surprised that she was willing to put up with his insanity. Then the Avengers were formed and Tony finally had more people who understood him as each of them wore a mask as he did to hide his true emotions.
He knew it would take sometime for all of them to adjust to each other but eventually they became a team and a family.
The person he was closest to was Bruce. They were science bros. He knew Bruce had self-esteem even lower than his own. Tony knew to help Bruce they all had to assure him that he was not a monster. tony believed there was more to the Hulk than just smashing.
He gradually saw a change in both Bruce and the Hulk. Bruce seemed to open up and relax more around the team and the destruction caused by the Hulk was more subdued and less. Tony also observed Hulk being extra protective of their team especially their eventually found the reason for this change.
Agent Clint Baton. One half of the assassin duo, archer and eyes of the Avengers. Tony didn't know Clint very well but as he got to know the archer, Tony found Clint's personality was similar to his own. Clint had a sarcastic humor that matched his own and he also enjoyed teasing his teammates. Clint and Tony became the Prankster Duo, taking pleasure in driving Fury mad. He also noticed Clint was very good at Computers and was a talented hacker. Tony had a hunch (he was sure that he was right) that Clint was as smart as him or Bruce whats with all those calculations needed to make perfect shots. Clint told him about how he was in the circus, that's where he developed his skills as an archer and that he went to University and studied Physics and Maths when he left the circus and was initially recruited in Shield.
Clint told him that Bruce was helping him recover from what Loki had done to him. The archer also told him that the team should do some team building with the Hulk. Clint told him that he had talked to Bruce about Hulk having more potential than smashing. Tony wholeheartedly agreed. Tony knew Bruce and Clint had formed a deep friendship with each other. But watching both of them interact he knew they liked each other as more than friends.
So Tony pushed Bruce to act on his feelings and tell Clint. He knew Bruce was holding back for the fear of hurting Clint until Tony pointed out to him how fond Hulk is of Clint and that Hulk would never hurt Clint.
One evening Tony returned from an SI meeting and went to the kitchen, there he saw Bruce and Clint locked in a kiss.
Tony silently backed out of the room happy for both his friends and silently applauded Bruce for taking his advice. He knew he had time to tease them later.