Yes but if one is more vigorous than the other it will swamp the weaker one.

Is this in the open ground, Maximusthegreat ?
If it's not and you're thinking of in a pot you'll need a very large pot.

Often looks wild and weedy, too, though that's not a handicap in a wilderness garden.

What were yuo considering growing. Roses up through a tree look good. Pyracantha with a summer flowering clematis Approx 5-6' high would work. There are lots of people on here who can advise you if you can say what you want to grow together.

I have an early clematis with a late honeysuckle. Clematis microcephla [feb] through a philadelphius.
Clematis Victoria through climbing rose New Dawn, both in flower now. Clematis tangutica late sumer through winter flowering jasmine. All doing well.

Great suggestions Scotsgran and Seaburngirl...
added this question to GoYpedia Climbing Plants... :o)