I too, have found it extremely weird that Jack Jr and Tam Jr have been married three and a half years and no kids/pregnancy, especially considering the flavor of Christian they seem to be.
Now, there is an exceptionally slim chance they are simply waiting to have children until they are in a better ter position financially, but I simply cannot see either of them being this responsible.
Jack Jr. also doesnt strike me as the type to practice wrapping it up. Tam Jr may be on birth control, but again, this doesnt seem to make sense as their brand of Christianity, while not forbiding birth control, tends not to use it in married couples who have no kids at all yet.
The other thing I can think of, is that they all knew about her brain tumor health scare much sooner then when Jack announced it, and they held back on procreation until Tam Jr's health had improved.
The most logical answer is that Jack Jr. Is such a raging homosexual, he is just creaming poor Tam Jr's hershey hole and hoping GodJesus gives them a miracle butt baby