On the matter of eggs and breasts, a little "reverse engineering" helps.
As I recall, John Carter and Dejah Thoris did have off-spring. At least I recall reading (wa-a-a-y back) at the beginning of one of the sequels when Carter was stuck on Earth and pining to get back to Mars and Dejah Thoris, his thoughts were not just on her, but also on an egg that was waiting to hatch. Perhaps the reproductive system of Dejah Thoris and other humanoid Martians is like that of the duck-billed platypus. The platypus lays eggs, and when they hatch, they suckle their young.
H. G. Wells' Martians in War of the Worlds were pretty ghastly critters, but if Martians were like this—hell, she could invade my planet any old time. Dejah Thoris.
On the other hand, I'm not sure I'd be too enthusiastic about this guy: Tars Tarkas