  We report low-temperature magneto-transport measurements of an undoped
Si/SiGe asymmetric double quantum well heterostructure. The density in both
layers is tuned independently utilizing a top and a bottom gate, allowing the
investigation of quantum wells at both imbalanced and matched densities.
Integer quantum Hall states at total filling factor $\nu_{\text{T}} = 1$ and
$\nu_{\text{T}} = 2$ are observed in both density regimes, and the evolution of
their excitation gaps is reported as a function of density. The $\nu_{\text{T}}
= 1$ gap evolution departs from the behavior generally observed for valley
splitting in the single layer regime. Furthermore, by comparing the
$\nu_{\text{T}} = 2$ gap to the single particle tunneling energy,
$\Delta_{\text{SAS}}$, obtained from Schr\"{o}dinger-Poisson (SP) simulations,
evidence for the onset of spontaneous inter-layer coherence (SIC) is observed
for a relative filling fraction imbalance smaller than ${\sim}50\%$
