Tancred's parents are supposed to be Bohemond's sister Emma and Odo the Marquis. So it has been stated by Ralph of Caen, a contemporary, who wrote a biography of Tancred called Gesta Tancredi. Amazingly, it has only just in 2005 been published in English, according to Google Books.
It seems the whole Guiscard family was fierce. Anna wrote, "(Contosephanus) overlooked his orders and sailed to Otranto, a city on the coast of Lombardy. The place was defended by a woman, the mother, so it was said, of Tancred, though whether she was a sister of the notorious Bohemond or not I cannot tell.......this woman gladiator by her talk and lying promises kept Contostephanus's plans in abeyance. Meanwhile the son for whom she was waiting did arrive, with attendant counts. He fought Contostephanus and beat him conclusively."(Book 12) Of course it is not surprising that Emma would fight since her mother Sichelgaita was known to put on armor and wade into battle with her husband Robert Guiscard, as Anna wrote "She went on campaign with her husband and when she donned armour was indeed a formidable sight."(Book 1) Sichelgaita, however, is not Bohemond's mother. He was the son of a first marriage to Alberada. Actually, I am not even sure Gaita was Emma's mother. There is a divided opinion on if Emma was Bohemond's full sister or half sister and if Alberada was not her mother as well.
Other comments about Bohemond include, "Bohemond, who was in any case a warlike man and loved danger". Or when he was facing Alexius in battle, Bohemond was tricked into racing ahead of his own troops in pursuit of the imperial standards which is where Alexius should have been. Then Alexius went and defeated Bohemond's troops while Bohemond was off on a mad dash. He was later found on an island on the river Salabria, eating grapes and bragging about how he had beaten Alexius, making a joke about the name of the place where the battle was - Lykostomion- when he was told that he had not. He jumped up, angry, and rushed back to fight. Eventually Bohemond did defeat Alexius, hence the animosity between the two, but Bohemond's progress towards usurping the Byzantine throne was stopped when Alexius send messengers to Bohemond's lieutenants pointing out that they had been fighting for four years and has Bohemond paid them yet. He did not have any money to pay them and, when his men figured that out, they went home and the party was over.
Anna also wrote of Bohemond, "Bohemond resembled his father in all respects, in daring, strength, aristocratic and indomitable spirit. In short, Bohemond was the exact replica and living image of his father. He at once attacked Canina, Hiericho and Avlona like a streaking thunderbolt, with threats and irrepressible fury. He seized them, and fighting on took the surrounding areas bit by bit and destroyed them by fire. Bohemond was in fact like the acrid smoke which preceded the fire, the preliminary skirmish which comes before the great assault, Father and son you might liken to caterpillars and locusts, for what was left by Robert, his son fed on and devoured." In short, he was like a force of nature.
You have to wonder, if Bohemond had more resources at his command to keep expanding his kingdom at Antioch, we would be speaking about him like we do about people like Napoleon, Charlemagne, Alexander the Great, Richard the Lionhearted or Julius Caesar. He shares some personality traits with all of these but he ultimately failed and has been largely forgotten. What a pity but I guess I should spare some pity for all of his victims as well. He was a warmonger after all.