Yep.
Are you new to how coaching works? Coaching is the biggest nepotism profession there is. I am not saying it is good or bad, but it is how it is. HC's hire assistants they are familiar with and know they can trust. They aren't going to fill their staff with guys they are just getting to know and can't fully trust.
Here are just some examples:
HC DMac brings Jay Norvell with him
HC Alvarez brings DMac to Wisconsin with him
HC Snyder brings Del Miller with him
HC Stoops brings brother Stoops with him
HC Kill brings NIU coaches with him
It isn't something that is unique to ISU coaches.