The term DEIMOS SIBLING is a reference to the two moons of MARS, Deimos and Phobos. The crossword solutions for this term are MOONS (5 letters), MARS (4 letters), ARES (4 letters), MOON (4 letters), BRO (3 letters), and SIS (3 letters). MOONS refers to the two moons of MARS, Deimos and Phobos, while MARS is the planet that these moons orbit. ARES is the Greek god of war, who is associated with MARS. MOON is a general term for any natural satellite that orbits a planet, and BRO and SIS are abbreviations for brother and sister, respectively, which refer to the relationship between Deimos and Phobos.