Okay... I saw this kinda touched on in a thread that has been locked BUT I really think it has a good point hidden in there.
We have so far seen Avatar Roku's castle and Kyoshi's shrine.?? Although there were numerous pieces of memorabilia at Kyoshi's shrine, there were no signs of a 'family life'.?? And although Fire Sage Shyu knew much about the history of the sages and spoke of Avatar Roku, he never mentioned anything of Roku having a family although he discussed his own family ancestory.
Now I know we haven't heard anything about other Avatars but it would appear to me that an Avatar leads a life of solitude.?? Is it because of their great responsibility of having to maintain balance or is it because if an Avatar were to have a family, that could be a simple of weakness (i.e. the Guru did say??Aang had to let her go).?? And if there were a weakness than of course, the Avatar could not be the most powerful bender on the planet because there would be a way to stop him/her.
Just a thought... feel free to speculate