dnd 5e – Can a controlled ghast be the leader of a group of ghouls?

I am creating a necromancer, and looking for the optimum number of undead to control, I searched the history of the monsters. Ghosts tend to be leaders in herds of demons. But nowhere can I find how he does it, or how many I can keep in order.

So that makes me wander. Can a controlled ghost be the leader of a pack of uncontrolled ghouls? And if you can, how many could you send?

That could significantly increase the amount of undead that my necromancer could control by indirect means.