Typically, you must separate them depending on your sex ratio.
How many hens will you have? The more femmes, the less of an issue it is likely to be.
Sometimes, as gritsar suggests, they will get along. But you have to wait and see what they do in the presence of breeding females.
Odds are that the 2 will fight incessantly, as long as there are a smallish number of girls around... in this case, smallish is anything below 15 or so. These are bantams, so they are a bit more high strung in general and the numbers shift a little.
Nevertheless, the lesser male will probably end up on the fringe of the flock if it is small. He will divide his time between dodging the dominant male, eating when he can and stealing whatever breeding opportunities he can.
It's possible he may suffer some for all this, meaning he won't make top breeding stock. If he does succeed at his clandestine trysts, you run the long-range risk of diminished flock vigor.
While that is probably not in your mind as an issue, in the sort term, they will bear watching.