The parents of Jane, their first(?) born, are shown as Robert Smith and Sarah Smith formerly Richards. Sarah was the informant (with a mark).
It is possible that either Robert or Sarah were in an undissolved marriage at the time of Jane's birth and thus unable to marry but ,as neither of them was more than 21, this seems unlikely. Perhaps I need to obtain the birth certificate of a later child to check on the maiden name Sarah gave at that time.
Census records suggest that Robert was born in Gelligaer circa 1827/8. Their children, as extracted from census records and matched to BMD index, appear to have been:- Jane 1847, Mary Ann 1849, (Morgan 1850?),Jennet 1853, (Gwenllian 1853?), Joseph 1855, Henry 1857, David 1860, Ann 1862, Sarah 1864/5.