All too frequently we always hear the Byzantine side of the story of the Latin Empire of Constantinople. Here I've translated from Old French an extract of a history by Baldwin of Avesnes on the Latin emperors as found in La Conquête de Constantinople pgs. 423-7 (which you can find online by clicking here).
Now that we have spoken to you a little about the emperor Frederick and the land beyond the sea [Outremer], we shall tell you about the empire of Greece.
You have heard above how the emperor Henry went to the kingdom of Salonika and of the war that he waged against the Lombards who wanted to hold the land in opposition to him. When he had vanquished them, he made peace with Johennis the king of Vlachia [Kalojan, the king of Bulgaria 1197-1207] and Toldre l'Acres [Theodore Lascaris, emperor of Nicaea 1204/5-1221/2]. He took as his wife the daughter of Kalojan and gave him in marriage his niece, while he gave another one to Theodore Lascaris, and a third one to King Andrew of Hungary [Andrew II 1205-1235]. These three ladies were the daughters of Count Pieron d'Auchoirre [Peter of Courtenay] and the Countess Yolent [Yolanda], the emperor's sister. By means of these marriages, he obtained peace and aid, though he did not live much long afterwards and died without any direct heirs, which was a real shame since he had been very vigorous and great-minded. The barons in Constantinople immediately then sent messengers to Peter of Courtenay, whose wife was the sister of the emperor. They were the German cousins of King Phillip of France. He had two sons by his wife. The eldest was named Phillip to whom he had given the county of Namur which had come to him by way of his wife when Phillip of Namur [Phillip I the Noble 1195-1212] died without any direct heirs. The other was named Robert. He had more daughters than the three we have told you about who were married off. When the messengers came to Count Peter and he heard of the death of the emperor Henry and how the barons were asking him to become emperor, he set his affairs in order and set out with his wife. Along with them went the Count of Sansuerre and a large company of knights and sergeants. When they came to Rome, the Pope crowned them. From there, they went to Brandis [Brindisi] and took to the sea. The Emperor Peter then came to Duras [Durres], which was one of the chief cities in Greece across from Sezille [Sicily], while the empress his wife went ahead to Constantinople because she was pregnant. She had not been there long before she gave birth to a son named Baldwin.
The Emperor Peter, meanwhile, who had gone to Durres, was received there with great honor by its lord, who was named Toldres li Communies [Theodore Comnenus Angelos, despot of Epirus 1215-1224, emperor of Thessalonica 1224-1230]. Yet, he had hardly been there long before he was seized hold by him along with the count of Sansuerre and held there in prison until they died. The Empress Yolanda did not live much long after either before she died at Constantinople. And so the barons of the land sent an entreaty to Count Phillip of Namur asking him to come become emperor as it had so fallen to him. When Lascaris learned that the emperor Peter had died as well as the empress Yolanda, his wife, he tried to conquer the empire and commenced hostilities. And so, the barons in Constantinople sent a large party of their people against him. The commanders of them were Sir Gerard la Truie and Gryu who reconquered a large part of the land that the emperor Henry had gained before them. Meanwhile, the messengers that came to Count Phillip of Namur told him that the barons were asking him to be emperor. He had no desire to go, so he sent Robert, his brother. He traveled by way of Hungary where he was received with great honor by his sister and was the queen of that land, and by King Andrew. He passed the winter there in Hungary because the way forward was uncertain. He had with him a sergeant who was born in Lille in Flanders. No one would say he was the uncle of Robert who was going to become emperor. Yet, he had a beautiful lady as his daughter, so Robert of Courtenay dressed her up richly and said that she was his cousin opening discussions of marriage between her and the king of Serbia [Stefan II 1217-1228]. The king, who desired the lady he saw, agreed to the marriage and their marriage was celebrated with great ceremony. Through this marriage and the aid of the Vlachs, Robert of Courtenay arrived safely in Constantinople, where he was received with much joy. However, he did not bring the father of the lady with him so that the affair should not be known, but gave him money and sent him back to Flanders. When Gerard la Truie and his men learned that Robert had reached Constantinople, they went to him and crowned him at Saint Sophia. After this, they undertook to bring about peace between the emperor Robert and Lascaris, who was married to his sister. The lady herself made a great deal over it bringing an end to hostilities and finally Lascaris agreed to give the emperor his daughter [Eudocia] who he had by his first marriage as a wife and lots of land to go with her.
This was agreed to by both parties and all of the prisoners were released. However, to be brief, when Lascaris died, Robert no longer wanted to go through with the marriage. The barons of the land felt great contempt for the marriage too, so they recommenced hostilities. The Cumans were fighting on the opposing side and laid siege to a castle on a mountain. The emperor Robert sent his best men there to defend it, but they were defeated and were for the most part killed off. This proved a great loss for the emperor because little remained of the folk with which he might do great things. At length, talks were reopened and a marriage between him and the daughter of Lascaris. A great number of prisoners were released too who were in le Gryu’s custody. For a time, the emperor Robert kept the peace. Yet there was a woman in Constantinople who was the daughter of knight from Artois named Baldwin of Nueville. The emperor Robert was in love with her so much that he abandoned the marriage between Lascaris' daughter and himself. Instead, he married this lady shamelessly and had her join him in the his palace along with lady's mother too.
When the French people in Constantinople found out about it, they were distressed and distraught because the emperor was not doing what he was his duty. On this account, they made a joint resolution and went to the emperor's chamber. They took the lady's mother and sent her on board a boat to be drowned, while they cut off the girl's nose and her lips and went away. When they emperor saw what his people had done, he could not stand to remain there and so he boarded a galley and went to Rome where he complained to the Pope about the disgraceful acts that his people had done to him. The Pope comforted him and soothed him, and then asked him to go back to Constantinople. As he was going back, he stopped in the land of Joifroi de Vile Harduin [Geoffrey of Villehardouin], who received him with much honor, but there he took ill and died from it. When those in Constantinople found this out, they held a counsel over what should be done. Several of them were for leaving the city, but another part of them said that it would shameful to leave such a noble city just like that.
At length, in general agreement, they sent messengers to the Pope informing him about the condition of the realm and asking him to advise them what should be done. In addition, they asked him to speak to King John of Acre and get him to defend the empire because they could not bear in the least to ask for aid from others. The Pope, who took pity on the realm, sent a message to King John asking him to fulfill this need. King John responded that he would do so in no manner because there was still one son left of the emperor Peter, who was outside of the realm, and that he had no desire to put himself in such grave danger to make safe another realm. The Pope told him if he would go there, he would provide with people and aid. At length, he said that he would go if it was agreed that the heir to the throne marry one of his daughters and swear an oath that as long as the king was alive, he would not demand power for himself in the empire, that the peers of the realm pay him homage, and that all the land that he would conquer that had belonged to the child's ancestors, would continue to belong to the child. If he conquered any other land, it would belong to his descendants who would hold it as a fief from the emperor. The Pope agreed to this and informed the messengers from Constantinople of it who returned to Constantinople and reported to the knights all that they had heard. They held a counsel and because they saw that the child was still young and held little land outside Constantinople, it seemed that they had little to guarantee, so they gave their approval to the agreement.
And so, they responded to the Pope that they accepted the agreement as it had been set forth. When King John came to the Pope, he gave him a lot of aid and swore to him that he would help aid with men. Then the king went to Venice and took to the sea for Constantinople. The knights went to meet him and received with great honor. In short, not long after, Baldwin would become emperor, was married to the daughter of King John and swore an oath to keep the agreement that had been reached and all of the people paid him homage. Now that we have spoken a little of the empire of Greece, we shall speak of King Louis of France.