The oldest child looks so done with her parents, LOL. I like how she's still combing the younger one's hair, she seems to be the responsible type. (^^)
If that's the case, usually I'd expect a bottle of mommy's breast milk(preemptively pumped so Eli can do the feeding). But we're probably putting far more thought into this than the artist ever did.
Given that most everybody refers to the gems as "she", I can understand someone expecting that tag.
But getting philosophical, if we run with the idea that the gems are mankind's "bones", then they would have sexual differentiation of some sort, given the difference between mens' and womens' skeletal structure. Kongou-sensei provides a nice demonstration of this(intentionally or not).
Great idea, but should last longer. Even just going at half the speed would be fine, doesn't necessarily need more frames.
Edit: Okay, I futzed with it a bit. Not sure what dynasty's policy on links is... but here. https://i.imgur.com/qpjbVzp.gif
Tried to give you a little time to view each image while still making the motion-y bits flow okay.