Meltdown and Spectre have both been announced at the same time, almost always in the same sentence. Is there a connection, other than timing and the fact that they attack chips? Are they used together in tandem to exploit a system? Or is it just coincidence that they were announced at the same time?
These are all attacks in the same area, i.e. using side channels during speculative execution in CPU's. It is not uncommon that if you find one problem you look deeper and find even more problems in the same area.