  We report measurements of the ratios of branching fractions for $B \to
\bar{D}^{(*)}\pi\ell^+\nu_\ell$ and $B \to
\bar{D}^{(*)}\pi^+\pi^-\ell^+\nu_\ell$ relative to $B \to
\bar{D}^*\ell^+\nu_\ell$ decays with $\ell = e, \mu$. These results are
obtained from a data sample that contains $772 \times 10^6 B\bar{B}$ pairs
collected near the $\Upsilon(4S)$ resonance with the Belle detector at the KEKB
asymmetric energy $e^+e^-$ collider. Fully reconstructing both $B$ mesons in
the event, we obtain \begin{align*} \frac{B(B^0 \to
\bar{D}^0\pi^-\ell^+\nu_\ell)}{B(B^0 \to D^{*-}\ell^+\nu_\ell)} &=
(7.24\pm0.36\pm0.12)\%\ ,\\ \frac{B(B^+ \to D^-\pi^+\ell^+\nu_\ell)}{B(B^+ \to
\bar{D}^{*0}\ell^+\nu_\ell)} &= (6.78\pm0.24\pm0.15)\%\ ,\\ \frac{B(B^0 \to
\bar{D}^{*0}\pi^-\ell^+\nu_\ell)}{B(B^0 \to D^{*-}\ell^+\nu_\ell)} &=
(11.10\pm0.48\pm0.20)\%\ ,\\ \frac{B(B^+ \to D^{*-}\pi^+\ell^+\nu_\ell)}{B(B^+
\to \bar{D}^{*0}\ell^+\nu_\ell)} &= (9.50\pm0.33\pm0.27)\%\ ,\\ \frac{B(B^0 \to
D^-\pi^+\pi^-\ell^+\nu_\ell)}{B(B^0 \to D^{*-}\ell^+\nu_\ell)} &=
(2.91\pm0.37\pm0.25)\%\ ,\\ \frac{B(B^+ \to
\bar{D}^0\pi^+\pi^-\ell^+\nu_\ell)}{B(B^+ \to \bar{D}^{*0}\ell^+\nu_\ell)} &=
(3.10\pm0.26\pm0.21)\%\ ,\\ \frac{B(B^0 \to
D^{*-}\pi^+\pi^-\ell^+\nu_\ell)}{B(B^0 \to D^{*-}\ell^+\nu_\ell)} &=
(1.03\pm0.43\pm0.18)\%\ ,\\ \frac{B(B^+ \to
\bar{D}^{*0}\pi^+\pi^-\ell^+\nu_\ell)}{B(B^+ \to \bar{D}^{*0}\ell^+\nu_\ell)}
&= (1.25\pm0.27\pm0.15)\%\ , \end{align*} where the uncertainties are
statistical and systematic, respectively. The invariant mass spectra of the
$D\pi$, $D^*\pi$, and $D\pi\pi$ systems are studied. Branching fraction
products are extracted, among them the first observations of $B(B^0 \to
D_1^-\ell^+\nu_\ell) \times B(D_1^- \to D^-\pi^+\pi^-) =
(0.102\pm0.013\pm0.009)\%$ and $B(B^+ \to \bar{D}_1^0\ell^+\nu_\ell) \times
B(\bar{D}_1^0 \to \bar{D}^0\pi^+\pi^-) = (0.105\pm0.011\pm0.008)\%$.
