Usually, yes, but not always! I'm 29 (born in 1993), which I think is pretty clearly in the range of millennial (definitions vary, and I've seen cutoffs anywhere between 1994 and 1997, but I don't think anyone would put me in Gen Z by any reasonable stretch of the imagination). My parents were born in late 1958 and early 1959, which is probably not within the most common definition of boomer, but I've met other people my age with parents born a few years before mine. I don't think anyone would consider someone born in, say, 1955, to be Gen X, and having a kid at 39 in 1994 would have been somewhat unusual but not really that crazy (especially if the other parent happened to be a few years younger).
If that still doesn't convince you, I don't think I have anything else I could say, but maybe reading this comic might provide a compelling argument: https://pbs.twimg.com/media/EOdaSW2XUAE1Pxm?format=png&name=...
I get where you're coming from but I think maybe relax a bit there...
OI. The parents of the millenials are the X-gens mate.
Sometimes known as the lost generation, or latch-key-kids etc.
The boomers are _our_ parents! And don't you forget it.
Now, get off my lawn :)