Based on the results of accurate variational calculations we demonstrate stability of the five-body negatively charged ions a + b + μ − e − e −. Each of these five-body ions contains two electrons e −, one negatively charged muon μ − and two nuclei of the hydrogen isotopes a,b = (p,d,t). The bound state properties of these five-body ions, including their hyperfine structure, are briefly discussed. We also investigate the hyperfine structure of the ground states of the four-body muonic quasi-atoms a + b + μ − e −. In particular, we determine the hyperfine structure splittings for the ground state of the four-body muonic quasi-atoms: p + d + μ − e − and p + t + μ − e −.