Zaphod is the DM of the Aztecs, but he is a relative (uncle) of Maybelline's. The father is most possibly a Young Ones rover, Homestar Runner, that was with her and the Aztecs for a few weeks, when Zaphod was roving. When Zaphod returned, he chased Homestar Runner away (he is still in the general area).
A relative can be the DM of a mob, when there is no mate yet, or anymore for the DF. The dominant pair can be a brother and sister (like in the Whiskers and the Lazuli now), a mother and son (after the DM passes, and before the DF finds a new mate), or even an uncle and niece (Zaphod and Maybelline, and Zaphod and Rocketdog before) etc. In this case (normally), the DF and DM do not mate. There was a case of a dominant couple, an aunt and nephew, that mated (I believe it was Eleusine and Dante).
Although I know part of Zaph's refusal to give up the DM crown is his personality and habit, I wonder how much of it is due to the fact that if he allows another to be DM he can be run off - as Frank was. It would break my heart if Zaph was run off.
Zaphod is respected and loved by his family, that is why he is still a DM. And of course, once a DM, always a DM! But a male outsider would dethrone him, and a lot of times male meerkats become seriously injured and die during a struggle for dominance. As for Dougal (MM's Houdini), did he have this fate as well? Did he disappear (died) around the time that wild male meerkats infiltrated his group, the Zappa, or later? I guess he was the DM at the time. Or he encountered male meerkats, from other mobs while roving? Does anybody know? Bischonmom, I think you are right. Zaphod, an experienced, older meerkat that witnessed a lot of these power struggles, knows the dangers of allowing another (especially younger) male in the group, that is why he fends off competition. In fact he is very successful at this. Male meerkats have better chances of survival when they are members of a group. Zaphod and Youssarian had a very special bond; they allowed each other to remain in the group, which is not so common. It would be terrible if anything happened to Zaphod, but he is fine for now. As for the two Young Ones rovers, they remained in the area, and they might join a mob, if they did not already. We might find out soon (FKM's January life history report).