Send people into the wastes, let them die, abandon them. Now they can have babies.
It is quicker to just build an execution chamber. One production room (doesn't matter which type). Assign the dweller you want to get rid of to your execution chamber. Strip them of all gear and meds. Rush the room over and over until they die. Then remove them.
Would be nicer if people just aged and died.
request a refund, delete the app and forget you ever played it.