I didn't read the novels but my interpretation would be that the two of them trusted the queerats because they helped them and after the baby was born they just killed them.

lol.. i wonder why they would even stick around rats..
also that doesnt make sense, because those rats always reported 99% of things they saw to the humans.
if maria and that other guy would've been with them, they should've got reported to the elders in the town.
and those would've killed them both.

**** logic

The rats helped them escape and I guess surviving alone would have been very tough
Squealer planned the extinction of the human race and therefore he needed the two of them. Reporting them to the humans woudln't make sense.

oh k
seems like maria and that weak guy deserved to die.