It's not like Sniper Joes are considered Proto Man's children.
And if we're talking about DNA, then wouldn't High Max and many of the X6 reploids/mavericks be considered Zero's children?
What the...does that even anatomically make sense? Her legs are absurdly long, given that Reploid boots usually go up to your knee.
also, DNA is basically the key core programming that makes a reploid who they are. it carries information such as their abilities, their type, and all that. it is basically the robot equivalent of DNA, and so, is referred to as such.
Reploids are loosely based off of X's internal structure. the big 4 are based off of his DNA, that is to say, his very programming. The stuff you get boss weapons from.
also, in that regard, I guess the X6 gate creations can be considered Zero's children, since they were made from his DNA, but somehow, it doesnt feel right to do so. Cyber elves are also technically Zero's children. His and Sigma's. (I say Zero's the mother.) They were derive from the sigma virus within Zero, after all.
Also, Sniper Just LOOK like Protoman, and loosely use similar tactics, but thats about it. the similarity is only skin deep.