Growing up in Vault 101 during a time when the vault dwellers ventured freely into the outside world, Alphonse's parents believed the vault should have no contact with the dangers out there. As he got older, Alphonse knew he had to correct the gross lapses in security. He got his chance when the Overseer - a strong proponent of outside contact - disappeared one day while out in the wasteland. Many suspected foul play, but the young, charismatic, strong-willed Alphonse Almodovar offered the vault dwellers new leadership, and they had little choice but to accept. 
In late 2258 or early 2259, Overseer Almodovar accepts James and his child into the vault, and James is assigned to be the new vault physician.
In 2260, Overseer Almodovar is widowed and left a single father when his wife dies from an unknown disease.
Unlike his predecessor, Alphonse Almodovar adopts a policy of isolationism for Vault 101: "No one ever enters. No one ever leaves.", and also "Everyone was born here and everyone will die here."
Almodovar is a widower with one child named Amata. He is very heartless to almost all of the vault residents, including the Lone Wanderer and James.
The dossier on Amata, located in the Overseer's terminal, reveals that he feels conflicted between his role as father and his role as overseer, attempting to find a balance between the duties that come with both. Despite his harsh and heartless interaction with all those who live in the vault, including Amata at times, it appears he desperately wants to connect with his daughter. He states that no matter what he tries Amata just seems to see him as "The Overseer".
Escape!: When James escapes, Almodovar thinks that the player had something to do with it, so he sends his security officers after him or her. He orders the death of Jonas after James' escape and interrogates his own daughter. Depending on whether or not he is killed, Amata will react differently to the situation.
There is a photograph of Alphonse and his daughter Amata in Amata's room.
During Trouble on the Homefront his computer terminal reveals that, after you left, the Enclave contacted the Vault in an attempt to gain access, but he denied them entry as he would not trust the lives of the Vault inhabitants to outsiders.
He will call you "young man" even if you are a girl during dialog in Trouble on the Homefront. Also, he's always identified as "The Overseer", even if he relinquishes the position to Amata. These are some of the many oversights the developers made in the player's interactions with Alphonse.
At your 10th birthday before you go to the reactor level, if you follow the Overseer he goes past the reactor, goes up some stairs and engages in a dialog with Officer John Kendall, during which he says "The only reason I came is because Amata's friends with the brat."
If you fight him during the quest Escape!, he will say "The Overseer will hear about this!" even though he is the Overseer.
If you do not fight him and instead agree to turn yourself in, he will confiscate your weapons and immediately use them against you.