In theory, only one transistor would turn on due to differences in Vbe, but practically, both will turn on, but by different amounts. The one that's turned on more will carry more current and get a further lowered Vbe, robbing yet more current from the other transistor, etc, etc.
You can do this more easily with mosfets (as long as you provide a gate voltage that well exceeds either's Vgs thresholds) but it is fraught with problems if you do it with bipolar transistors.
And that's both in theory AND in practice.