A main theme of the show is the brothers' abilities and success in dating. Alan is very shy when it comes to women, and he has had several long-term relationships end badly. This makes him the polar opposite of his brother Charlie, who can get any girl he wants but rarely sees women after he sleeps with them (though he has also had some longer relationships conclude in rather unhappy fashions).
Alan used to be married to Judith (Marin Hinkle), who is the mother of their son Jake, and after they divorced Alan got stuck with paying her $3875 monthly alimony, Judith lived a luxurious life on Alan's alimony until she got remarried to Dr. Herb Melnick (also known as Greg Melnick in earlier episodes), Jake's pediatrician (Ryan Stiles). Alan was so overjoyed at the end of his alimony requirement that he had a large cardboard check made for her for the last payment. Following the wedding, he only had to pay child support.
Alan's second wife, Kandi (April Bowlby), was one of Charlie's old girlfriends. She's known for being so incredibly stupid that she makes Jake look like an intellectual. In the divorce, she received Alan's condo which they bought with the casino winnings they earned right after their impromptu Las Vegas wedding.
Alan drives a Volvo station wagon and runs his own chiropractic care clinic out in the San Fernando Valley, though he gets irritated when people point out he is not a medical doctor. Alan lives in the guest room of Charlie's house. He did not pay any rent for the first 5 years, 2 months and 11 days that he was living there, probably because all of his money went towards alimony and taking care of Jake; when Alan's mom said she would pay for Jake's college education, Alan had no incentive to go to work and felt aimless. He then agreed to fork over some money to Charlie every month, though the amount that would earn him a say in the household's operations was too high for him.
Alan's first wife and the mother of Jake is Judith. She is generally portrayed as humourless, bitter and hypocritical. Judith told Alan that the reason they were separating was because it wasn't working out, but then later told Alan that she had realized she was a lesbian...only to change her mind again later.
Alan and Judith met as teenagers at school and married at a young age. He lost his virginity to her during one of Aerosmith's songs (From the ep. Who's Vod Kanockers?) During the separation Alan desperately tried to get back with Judith, as he was seeming to think that they were getting along again, but it turned out that Judith was only using Alan to do her chores. Judith clearly depises and takes every chance she gets to humiliate Alan, even though it is sometimes clear that Alan and Judith still have feelings for each other. An example is that she says "I disliked you when we were married, I resented you, when we were divorced, but I only started hating you when you started sleeping with a girl half your age". In a Season 5 episode, Alan begins dating a divorced woman who is friends with him and Judith but keeps having visions of Judith and Herb making love, leading his date to say that he's not over Judith. Alan and Judith dated once more after the divorce, but kept failing to get intimate because of Jake interrupting at the wrong time, causing Alan to have to hide. When they finally do get a chance to get intimate, Alan becomes upset afterwards because Judith has learned some new moves in bed since the divorce. Alan starts another fight with her when Jake starts to walk into the room, causing Alan to jump out of the second story window and land in a thorn bush. When Alan gets home, he then realizes why he and Judith do not need to be together because it is always constant fighting.
During the divorce proceedings, Alan nearly lost all of his possessions due to Charlie sleeping with his attorney (Heather Locklear) and then breaking up with her; forcing him to fire her before the settlement could be finalized and find a new lawyer. Judith gets remarried in "Smooth as a Ken Doll" to Dr. Herb Melnick, Jake's pediatrician. Since that day, Alan may only be paying alimony to his second wife Kandi, a relief since there was some time before Judith remarried that he had to pay it to both Judith and Kandi. It is possible Alan does not pay Kandi alimony because she now makes much more money than he does, and that she signed divorce papers because she wanted to safeguard her earnings from Alan and probably being the smartest thing she has ever done.
In Season 6, Judith threw Herb out of their house and later slept with Alan, but their reconciliation ended when Alan realized Judith had not changed from the angry, irrational person who had divorced him. Judith later told Alan that she and Herb were expecting another child, leaving a horrified Alan to calculate whether or not he is, in fact, the biological father. However, his fears were assuaged after Judith stated the father was Herb and threatened to kill him if he revealed their affair.
Alan's ex girlfriend, Kandi, was one of Charlie's old girlfriends, who Charlie originally dated as a backup in case something went wrong between him and his girlfriend Mia. When Kandi came looking for Charlie, she met Alan, and they fell in love. They married, but divorced later, because Alan didn't want any children.
When Alan decided that he wanted to have children with Kandi they had not officially signed their divorce papers. Kandi then heard that she had a main role on a TV series, called Stiffs, and said that "nobody wants to see a pregnant "fornesic" scientist" before signing the papers that ended their marriage. Their married life was never shown in episodes, lasting only between the third and fourth seasons. She was not seen or mentioned in Seasons 5 and 6.
While he is a confirmed heterosexual, it was suggested multiple times throughout the series that Alan might be Bisexual and/or Metrosexual. In "Tucked, Taped and Gorgeous", Alan started to think about being gay himself after meeting a gay man named Greg in his single-parent support group. After meeting the man a couple of times, Alan got congratulated by most of his loved ones for finally "coming out". Alan found himself thinking this could be the reason he's had so many failed female relationships.
At the end, Alan decided to kiss Greg to check if he was gay once and for all. When he tried to kiss Greg, however, Greg told him that Alan was definitely not gay, as he said he knows gay men...and that even if he was, "which you're not" he would state again, he doesn't find Alan attractive at all but finds Charlie "pretty". Alan jealously told Greg to get out of his car and drive away. Though relieved that he wasn't gay, Alan mentioned that he felt that "I was letting a lot of people down". 
- ↑ "Phase One, Complete". Lorre, Chuck; Aronsohn, Lee; Beavers, Susan; Foster, Don. Two and a Half Men. CBS. 2003-11-17. No. 9, season 1.
- ↑ "David Copperfield Slipped Me a Roofie". Lorre, Chuck; Aronsohn, Lee; Roberts, Mark; Foster, Don. Two and a Half Men. CBS. 2009-02-02. No. 14, season 6.
- ↑ "Two and a Half Men". Trivia. The Internet Movie Database. http://www.imdb.com/title/tt0369179/trivia. Retrieved May 27 2008.
- ↑ 4.0 4.1 "Humiliation Is a Visual Medium". Lorre, Chuck; Aronsohn, Lee; Roberts, Mark; Gorodetsky, Eddie. Two and a Half Men. CBS. 2006-01-23. No. 13, season 3.
- ↑ "Smooth as a Ken Doll". Lorre, Chuck; Aronsohn, Lee; Gorodetsky, Eddie; Beavers, Susan; Foster, Don. Two and a Half Men. CBS. 2007-04-09. No. 19, season 4.
- ↑ 6.0 6.1 "It Never Rains in Hooterville". Lorre, Chuck; Aronsohn, Lee; Roberts, Mark; Foster, Don. Two and a Half Men. CBS. 2007-03-18. No. 18, season 4.
- ↑ "Tucked, Taped and Gorgeous". Lorre, Chuck; Aronsohn, Lee; Roberts, Mark; Foster, Don. Two and a Half Men. CBS. 2007-04-23. No. 21, season 4.