I've never seen anyone talk about this before so I think it's better to ask for a straight answer, can Asic miners do double mining? I know its possible on Graphic cards but is it possible to mine two different coins on an Asic miner? For example BTC + BCH or BCD.
If different coins have implemented in their code the same mining algorithm, same hardware and probably same software should be able to mine any of those coins at a time.
If, on the other hand you say about merged mining, ie mining both
in the same time, I think that it's not only that they have to the same algorithm, I think that they also have to have
something extra implemented to allow merged mining. Plus the mining pools may also have to know about it.
I have some old memories on the early days of Litecoin + Dogecoin merged mining, but they're fuzzy, so better explanations may be needed.