  In this paper, we study the fine Selmer groups of two congruent Galois
representations over an admissible $p$-adic Lie extension. We show that under
appropriate congruence conditions, if the dual fine Selmer group of one is
pseudo-null, so is the other. Our results also compare the $\pi$-primary
submodules of the two dual fine Selmer groups. We then apply our results to
compare the structure of Galois group of the maximal abelian unramified pro-$p$
extension of an admissible $p$-adic Lie extension and the structure of the dual
fine Selmer group over the said admissible $p$-adic Lie extension.
