‘Jihad by family’: Why are terrorist cells often made up of brothers?

Militants often call each other “brother”, and refer collectively to the “brothers” in Syria, Afghanistan, Iraq or France. Why?

Partly this is to indicate solidarity, attachment to a common cause, a sense of shared identity and endeavour. Partly it’s because that’s how young men speak, all over the world, but particularly in the kind of environments from which many contemporary militants come.

But it is also because, remarkably often, the term is entirely accurate. Those speaking of being “brothers” are indeed blood relatives, children of the same parents, who often grew up together.