If I had to do this, I would not connect the beams with thru the web bolts. If you really need both beams for strenght and the load is not symmetrical you will have a problem, because I´m not so convinced that they will share the load. As has been stated above, it depends on many things.
I would have tought about connection plates on the flanges. If the load is not symmetrical, you will end up with torsion on the built up section. I think this arrangement is more adequate in that respect.....