Good luck with that one. It's rather like saying it's a "fact" that there's only really one US President, who's variously white, single, and in his 40s; black, married with daughters, and around 60; and who's black, widowed, with a single son.
Muslims have traditionally said we have the same god, but that Xians and Jews screwed it up. Jesus wasn't crucified, but imperfectly revealed a God with no partners--no son, no trinity. "Jesus is God" is blasphemy. It's all in "they screwed it up", so we Xians and Jews worship a warped image of the one true God. They're tolerant. But Muhammed has it all over on Jesus. Xians used to consider Muslims heretics early on.
Xians believed, at one point (or at least some did), that Jesus was pre-existent to his birth and was the law-giver of old. In other words, Jesus was Yahweh. Chew on that one. Jehovah was skewered by a Roman soldier. But even then they believed in a triune god. That is, the Muslims are all wet. But it was a nice fiction because otherwise you'd have had genocide.
Not all Xians even believed that. "God" in some sense was the lawgiver, but didn't really mean it. Somehow.
Jews believe in a single G-d. No Jesus. Their G-d has no son and Jews missed the boat. That became offensive (in my lifetime).
I figure that Abraham knew Jesus and that's who told Abraham to spared Isaac. Er, Ishmael--in one tradition Abraham was going to sacrifice one son, in another a completely different son. Rather like insisting that my Barack Obama's kid's "Michael", and he has no daughters. (What, you say we don't have the same president? Who's yours, if not Barack Obama?)
It's only a "fact" as long as "fact" can mean "without foundation in anything observable or provable." In other words, it's only fact as long as it's not obviously able to be a fact but an assertion rooted in unprovable belief.
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