Three temperature-induced phase transitions at T=T₁, T_M/T_A, and T_C, related to the ferromagnetic order of the martensitic phase (FMMP), martensitic (structural) transitions (MT), and the ferromagnetic order of the austenitic phase (FMAP), respectively, have been observed in the off-stoichiometric Heusler alloys, Ni_50-xCo_xMn₃₅In₁₅ (x=1, 2.5) and Ni₄₅Co₅Mn₃₇In₁₃. The phase transitions temperatures are found to be depended on alloy composition. A kinetic arrest of the AP was observed for Ni_47.5Co_2.5Mn₃₅In₁₅ in the magnetization measurements during field-cooling cycle (FCC) at 50 kOe. Depending upon the cooling protocols, ZFC and FCC (at H = 50 kOe), two different ground states of the alloys can be found in Ni_47.5Co_2.5Mn₃₅In₁₅ and Ni₄₅Co₅Mn₃₇In₁₃ alloys. The ground states (T=4.2 K and external field H=0) of the alloys was found to be characterized by three main line: two, partially overlapping, at higher frequencies (300-450 MHz), most likely corresponding of manganese resonance lines and one at lower frequency at about 200 MHz. A significant shift in the spectrum of Ni₄₅Co₅Mn₃₇In₁₃ by about 100 MHz to higher frequencies was observed. The correlation of magnetizations obtained from magnetic moment and NMR studies is discussed.