Classic Twin Bunk Beds
There are many parts that are common between the upper and lower bunks. Check the exploded views for the details on which parts are the same.
The first in a series of three different bunk bed styles. This is what I would call the classic bunk bed. Two twin beds stacked vertically one on top of the other.
The two beds separate to be used as two separate beds as situations change in your household. When sitting side by side the upper bunk will still have rails around the bed.
The side rails attach to the legs with standard bed bolts that are hidden by faux tenons on the outside of the legs.
The bed project is full of mortise and tenon joinery. A simpler method mortise and tenon for all of the rail slats would be too cut a single groove on the rail and the fill between the slats with the appropriate sized spacer blocks. The end appearance will be the same and it will save you having to make 102 mortises. In addition I tapered the ladder rails so the steps are easier to climb and becomes very sturdy.
This is a practical and useful project that will be a hit with your family.