From help(brnn)
$theta
A list containing weights and biases. The first s components of the list contains vectors with the estimated parameters for the k-th neuron, i.e. ($w_k, b_k, β_1^{[k]},...,β_p^{[k]})'.$
when you looked at the str you saw two lists of equal length. The first should be weights and the second biases for each neuron in the model, since that's the order described. Run some of the examples given and see if your out$theta is similar in form. It's possible that the model was mis-specified.