It has been said in the TTV Podcasts that there are families in Brickonicle, which implies some form of natural reproduction (mother+father=babies). However, they have never addressed the idea of mixed elemental races. For example, what if a male Earth Matoran and a female Water Matoran were to marry and have children? Would the children only inherit one element, or would they become hybrids?
This topic is only relevant if the first sentence in this topic is true.