Strong, Mullen, and Whittingham have the strongest ties.
But I'd say Gary Andersen has stronger ties than Charlie Strong.
I don't think his tree is all that impressive, though Ryan Day is definitely performing well in his initial season as a head coach.
Where Meyer brought him back to Utah, where he was an assistant pre-Meyer, after a failed head coaching stint at Southern Utah.
Strong is closer to Whittingham. Like Whittingham, Strong was the DC when Meyer was hired, and he kept him on. Only Meyer had a previous history with Strong at ND, as well as other Holtz/Davie connections. Both of them have stronger connections than Andersen, who also was essentially inherited but only but given a reduced role than what he had before (no ST or AHC title). Also, it's easier to keep on a position coach. There's greater responsibility on the coordinators, so there is likely greater evaluation going on from the head coach in deciding to keep a coordinator of a failed regime--which he did with Strong and Whittingham.
Mullen has the strongest ties as someone who grew up under Meyer. Guys who got their break under Meyer seem strongest. That would include Day and Herman.