Millenia ago in the Fable Lands, a prince consulted a witch on how he was to find true love when his staggering wealth was all that seemed to be attracting princesses. The witch then transformed the prince into a Beast, ensuring him that true love's kiss could free him from his curse. Eventually, Beauty found him and the couple married.
Unfortunately the couple lost all their wealth when they fled the Fable Lands for the Mundane world and Beast was forced to take up a low paying job as a superintendent while his wife worked in a book shop. Nor was the curse entirely lifted as Beast's form was subject to his wife feelings towards him. If she was angry with him, he took on a more bestial appearance. Despite these trials, the couple has remained together and very loving down through the centuries, though Beauty does henpeck Beast on occasion.
When Bigby Wolf left office as Sheriff and Spymaster of Fable Town, the newly elected Mayor Prince Charming offered the office to the Beast (while offering the office of Deputy Mayor to Beauty). Like most of Fable Town, Beast had no knowledge of Bigby's clandestine activities and was initially staggered under the weight of the job, but he quickly recovered and has come to enjoy it. He has also formed a friendly relationship with the most powerful of Fable Town witches, Frau Totenkinder, who has altered Beast's curse to allow him to shapeshift into bestial form at will rather than being subject to Beauty's emotional state. (What he may or may not know is that Frau Totenkinder was the witch who cursed in in the first place.)
While initially reeling at the complexities of the job (much of what Bigby did was covert and unknown to the general Fable population), he has grown into the job and appears to even enjoy it. Beauty took Snow's position as Deputy Mayor, and has learned to cope with all of the responsibility. Early in her tenure, Prince Charming tried to seduce her, but she refused him, threatening to send her husband after him if he tried again. It is notable that Beauty realized, as a result of remarks made by Prince Charming during this seduction attempt, that her actions and words toward her husband were not generally as kind as she herself perceived; she subsequently resolved to be nicer to Beast. Although she made peace with her husband, he (still loving her very much) denied all her thoughts on herself being shrewish and cruel to him.
Beauty never knew that Bufkin had seen and heard everything that happened with her and Charming. Worrying about either Beast's wrath or Beauty's, he began to act very hostile around Beast, something Beast found odd. After the arrival in Fabletown of the Imperial Emissary, Lord Hansel, during the Sons of Empire story-arc, and the subsequent need to keep track of both him and his staff, Beast asked for, and was given, additional funding and manpower, plus was later assigned zephyrs, provided by Bigby Wolf's father, the North Wind, to act as spies. During the war against the Empire, as depicted in the War and Pieces arc, Beast remained in Fabletown, commanding the troops stationed there in case of a retaliatory assault by the Empire.
It is possible that Beast, eventually caught on about the kiss between Beauty and Charming. After his funeral, Beast pointed out to her, that she did cry an awful lot. While she merely brushed it off about being a crybaby at funerals, Beast still pointed out her crying. Beauty seemed a bit outraged, and reassured her husband that nothing happened between them. Though he did believe his wife, he pointed out again, she did cry an awful lot. This didn't seem to affect the couple much afterwards, as they were still together and would soon get a very big surprise.
According to the answers given in the Burning Questions issue, both ask Frau Totenkinder what it is she's knitting. When she answers she's knitting a garment for their firstborn child. To which Beauty laughs saying she's not even expecting, to which Frau answered "All things in time" and then offered to show them the progress of her knitting. Upon hearing them agree, she presented them a cute light greenish-blue footed pajamas with a lion head sewn on the front. In addition that the footed pajamas had four arms, two legs, and a place for a tail, indicating that their child might be a monster or at least have Beast's transformation problem. Upon seeing her work, this left both Beast and Beauty flabbergasted.
But with the destruction of Fabletown by Mr. Dark, its revealed that Beast had brushed off her gift as a joke. However, Frau's predication is shown to be quite true. As shown in the Great Fables Cross Over, after having a brief argument with Beast about his behavior with Bigby, Beauty and her husband are shown in their tent together having make up sex. While Beast was very happy from it, Beauty herself couldn't help but feel that there was something more special about and perhaps magical.
Later on in a next issue, she's revealed to be pregnant. While Beauty's absolutely extatic, Beast confesses to Bigby he's a little worried. In Fables #100, the child is a couple of week premature, but Beauty comes with the birth with a few complications. The child, a little girl is born normal, though sometime later it is shown that when she becomes angry, she undergoes a tranformation into a six limbed, tailed beast. Something Frau most likely forsaw and knitted the garment. Since the birth of little Bliss, her father has not been able to transform into his beastly form. When looked over by Ozma with her powers, she could not detect any trace of his ancient curse. A theory, currently unproven, is that the Beast's daughter has adopted his curse as her own. So far he and Beauty have not yet realized Bliss can transform.