The point is you are paying for one bed, one living area, one bathroom, whether you are a single traveller or as a couple. I’m in a hotel room at the moment with a bed and a sofa, can host 4 people or me, it’s the same size. At breakfast I usually sit on a table which can seat 4, but certainly one that can seat 2. I use almost all the resources a couple do, and spend less at the bar in the evening, so I’d expect to pay the same or even more.

Hostels often offer private rooms, to varying degree of privacy. But i've certainly stayed at hostels that offer very comfortable single private rooms with private bathrooms for a third the cost of a local hotel room. Expensive for a hostel, but great value for the privacy.

But if you're traveling with your family, just get hotel rooms. Hostels only came up in the first place in response to a gripe about solo travel.