Census enumerators are sometimes given a slightly incorrect detail or two to make a family situation appear different than it is. In this 1930 enumeration the husband’s “age at first marriage” is incorrect–probably to make it look like he was the father of all the children. The oldest child was the wife’s by a previous marriage.
There is not really anything in this enumeration to suggest that either–the gap in ages of children could easily be explained by an infant death, miscarriage, etc. This is why looking at more than one record is imperative.