"This Be the Verse" is a blunt, in-your-face send up of parenthood.  It's British colloquial ("mum") and modern vulgar ("They f*@# you up") in its conversational voice spoken by a swaggering male persona who seems to have a pint in one hand and a pen in the other.

But, there's depth in the poem.  It reminds me of the Greek tragedy Oedipus, whose parents, as you know, really f-ed him up by crippling him and leaving him for dead.  His fate were those broken ankles that he hobbled on all the days of his life.

Larkin, like Sophocles with Oedipus, knows that the only fate is not controlled by the gods, or oracles, or curses, but simply by blood, genetics, and "mum" and "dad."

He's saying your parents curse you like they were cursed.  Your vices were their vices.  Your suffering, theirs.  They went through it with their parents, the Victorians in their "hats."  And your kids will go through it with you: it's inevitable.  You end up just like your parents, even though your try to escape it.  And you raise your children the same way you were raised.  It's generational revenge: torturing of one generation by the next, out of spite.

He's saying if you want to stop the cycle, then stop having kids.  It's not a moratorium on parenthood so much as a wake up call for kids to realize this before they become parents.  He wants his audience not to pass on the suffering, but learn from it.  Trace it back.  Share it.  Get those skeletons out of the closets.  Stop repeating stubborn age-old mistakes.

In the last stanza, he wants his readers to be like little geologists:

Man hands on misery to man. / It deepens like a coastal shelf.

Family tragedy is buried in the blood, in experience, like fossils in the geological layers.  Like Oedipus, we must suffer to know it and stop it--not by not having kids, but by not crippling them at birth.