If you look at the proportions you'll notice that the bottom pony is not even halfway shown, so how are you getting "mother and son" from this? Not only is the bottom character obviously female and only slightly smaller in statue, the character above is clearly male ( snout and body frame)...and look at his expression. For that matter, look at BOTH of their expressions. Would a mother and son look at each other like THAT?
This is desire ( Look at how intently the top character is gazing into her eyes ). Desire mixed with anticipation and a hint of nervousness (the bottom character's wider eyes reflect the nervousness).
Now I can see it. I didn't think those were wings on the bottom, thought it was odd looking legs Originally I thought it was a mother wishing a daughter a good night sleep. Now everything has changed. Thanks for clearing it up.