In this work, we investigate the semileptonic decays of
$$B_{c}$$
meson to
$$\eta _{c}(1S,2S,3S)$$
,
$$\psi (1S,2S,3S)$$
and X(3872) within the framework of covariant light-front quark model (CLFQM). We combine the helicity amplitudes via the corresponding form factors to obtain the branching ratios of the semileptonic decays
$$B_{c}\rightarrow \eta _{c}(1S, 2S, 3S)\ell \nu _{\ell }$$
,
$$B_{c}\rightarrow \psi (1S, 2S, 3S))\ell \nu _{\ell }$$
and
$$B_{c}\rightarrow X(3872)\ell \nu _...
