Similar situation in my house growing up. Seven people, 1 shower. If you were not expedient, Dad was pounding on the door. If you were not efficient, tough.
Hair drying was done in your bedroom.
My current home has 3 bathrooms; two for the kids, and a master bath for my husband and I with a separate shower and tub. No lines, no pounding on the door.
Oddly enough, I can still wash my hair, body, brush my teeth, and dry off in five minutes if needed. The habits of youth don’t die.
We have 2-1/2 baths now. No pounding, no waiting.
We are empty nesters now, and as much as I love my kids, and loved raising them and all the crazy activities that come with that, I sure enjoy having just the two of us to take care of now. When the kids visit, it’s wonderful, too, but we are happy to be getting near retirement. Just a few more years.