Breaking up your workout

Breaking up your workout will not disrupt your gain really. It is harder to do with say resistance training because it is hard to hit the same muscles multiple times in a day, of course some programs promote this kind of training. As far as cardio goes it should be fine, just depends on how your knees and shoes feel. I have even seen programs that advocate breaking up the cardio in a similar fashion.

It depends on why you're doing 60 minutes of cardio a day.

If you were trying to improve your cardiovascular endurance, then it would be better to do it all at once, as 60 consecutive minutes is more of a challenge than 30 minutes here and 30 minutes there.

But you indicated your goal is weight-loss. If you're just trying to burn calories, it doesn't really matter. You may burn a few more by doing it all at once, just by virture of keeping your heart rate elevated for a longer period of time. But it won't be significant enough to make it worth rearranging your schedule.

I might suggest, though, that if you frequently find yourself having to break up 1 hour into 3 or 4 increments because of other obligations, you should try doing higher intensity cardio for a shorter duration. I think focus and consistency are critical, and it's hard to imagine you being really zoned in if you are being interrupted every 20 minutes by a screaming child. So just do 20 to 30 minutes of really intense work, and you're done.