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.
Arcana Coelestia #533
533. Since nothing further is mentioned about Lamech apart from the fact that be beget sons and daughters, who are the conceptions and births of such a Church, there is no need to pause any longer over him. What these births, or sons and daughters, were, becomes clear from the Church, for the character of a Church determines that of its offspring. Both those Churches called Methuselah and Lamech breathed their last just before the flood.