There isn't a built-in way to deal with multiple repositories at once, and if you think about the distributed nature of git, there really isn't anything but social convention that can define that. (Consider, what if someone pulls from you in one repository, but another remote for the second - can you have this coherence?)
You might find a tool like mr, which works with multiple repositories at the same time, helpful.
If you really have things that are tied that tightly, though, I would advise you to put them into one repository. That way you can't forget any of the steps, because they happen in one atomic operation.
If your code isn't actually that tightly tied together, though, then give up the "must branch at exactly the same time" notion and you will be happier.
与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…