I was reading the Holy Torah and I couldn't understand some parts, and it's maybe because I'm still lost in history. But the story said that in the land of Palestine, God had helped the children of Israel (his children) up with the Canaanite in the war that happened then, and with all the other cities and groups over there, and the only ones that lived on that land (the land of palestine) is just the ken of the 12 children of Jacob. So is it true?

Let's start by understanding that Abraham bought that land (the Biblical land of Israel) from Ephron the Hittite. Abraham was actually just interested in buying the Cave of Machpelah to bury his wife, but Ephron wouldn't sell him just the cave. He made Abraham purchase the entire country. This is, in fact, the oldest recorded land sale in history.

Now... approximately 250-300 years later, his great-great- grandchildren returned to the land that he purchased. According to the census of the period, taken at the time that the Israelites re-entered the land, the number of males between the ages of 20 and 50 (military age), fit for service, was roughly 603,550. Extrapolating the number of women, and the number of men below the age of 20 and above the age of 50, and those unfit for service, the total population was roughly between 2 million and 6 million, depending on who's opinion we accept.

So even though we are talking about the descendants of Jacob's 12 sons, we're talking about a LOT of people.

Hope this answers your question.