Arcana Coelestia #1147
1147. 'And sons were born to them' means matters of doctrine deriving from those three. This is clear from the meaning of 'sons' in the internal sense as truths of faith, and also as falsities. Consequently matters of doctrine, both true and false, are meant, for such are the doctrines of Churches. That 'sons' has such a meaning, see above in 264, 489, 491, 533.
Isaiah 66:7-9
7
"Before she travailed, she brought forth; before her pain came, she delivered a son.
8
Who has heard such a thing? who has seen such things? Shall a land be born in one day? shall a nation be brought forth at once? for as soon as Zion travailed, she brought forth her children.
9
Shall I bring to the birth, and not cause to bring forth?" says Yahweh: "shall I who cause to bring forth shut [the womb]?" says your God.