  We analyse the signal sensitivity of multi-lepton final states at collider
that can arise from doubly and singly charged Higgs decay in a type-II seesaw
framework. We assume triplet vev to be very small and degenerate masses for
both the charged Higgs states. The leptonic branching ratio of doubly and
singly charged Higgs states have a large dependency on the neutrino oscillation
parameters, lightest neutrino mass scale, as well as neutrino mass hierarchy.
We explore this as well as the relation between the leptonic branching ratios
of the singly and doubly charged Higgs states in detail. We evaluate the effect
of these uncertainties on the production cross-section. Finally, we present a
detailed analysis of multi-lepton final states for a future hadron collider
HE-LHC, that can operate with center of mass energy $\sqrt{s}=27$ TeV.
