Ian Gallagher is 6'0 feet high and has red hair. He changes his haircut several times througout the series. His clothes are mostly old ones from his brother Lip, which annoys him, but he doesn't complain much about it.
His family is very important for Ian. Although his father is drunk all the time and they're barely getting by, he still likes his life, mainly because of his family.
Ian and Mickey started off as enemies, because Mickey thought Ian raped his sister Mandy, which turned out to be false later. Mickey also tended to steal from the shop Ian was working in. When the owner of the shop, Kesh, threatened Mickey with a gun, Mickey stole it and Ian tried to get it back. The fight that followed surprisingly ended in rough sex, which marked the beginning of them being fuck buddies. Afterwards Mickey returned the gun, but when Ian wanted to kiss him because of it, Mickey threatened him. When Ian's mother Monica returns to the Gallaghers with a plan to take away Liam, Ian needs a break from his family and meets with Mickey in the shop to fuck. Kesh catches them and shoots Mickey in the following scene, and Mickey goes to jail because of theft from the shop. Kesh's and Ian's relationship is officially over after that. Ian visits Mickey several times while he is in jail, but Mickey clearly shows his disgust towards Ian's attempts to show affection.
Ian and Lip always had a good relationship. They are not only brothers, but also best friends and partners in crime. Even if they occasionaly have serious fights, they still love and trust each other.
The first one to know about Ian's homosexuality was Kesh, the owner of the shop Ian worked in. Even though Kesh was married, he was in a secret relationship with Ian.
Ian also mentioned a boyfriend he had before Kesh, but that boyfriend never appears in the show.
His brother Lip finds out second when he notices a gay porn magazine in their room. He tests Ian by letting Karen give him a blow-job, and Karen says that Ian didn't get hard. Later in the episode, Lip catches Ian and Kesh having sex in the shop. He's angry because Kesh is married and much older than Ian, and he also thinks that his brother prostitutes himself to Kesh. After Ian explains to his brother that Kesh and he love each other, Lip accepts their relationship.
A few episodes later, Mandy is flirting with Ian and gets angry when he doesn't want to have sex with her. For revenge, she tells her brothers that Ian raped her, but after he explains to her that he's gay, she calms down and they become friends.
After nearly going to jail at the end of season 1, Ian outs himself to his sister Fiona, who says she knew already.
His father Frank finds out when he catches Ian and Mickey fucking while stealing from Ian's shop.