My interpretation, for what it is worth is that the Ipso term "brothers" represents the two groups of Ipsolstai encountered to date: Group 1, the Ipsos on Mars, Burn's brothers. Group 2, the Ipsos on Titan (maybe), the other brothers. Burn's brothers, the ones who have had extensive dealings with our probes, have come to acknowledge the sentience of the probes and theirfore their right to exist. The other group has not dealt with the probes, except for threatening Zachary and pushing him into the groove, fear the probes (remember, the amphibeans were proceeded by mechanical entities) and thus want the probes destoyed.
Taz