I think kids instinctively know who their siblings are. How else can I explain why Megan can tolerate Ryan's rough ways in handling her?
First, it was just sticking his finger into her mouth which she would suck on happily. I almost fainted when I first saw it. All my shouting and scolding did not make Ryan do this less and Megan did not seem to mind, so I left it.
And then there is the wriggling of the nose. Ryan wriggles her nose so much and so hard, I am afraid it will fall off one day. Again, despite us thinking it must be annoying, Megan actually loves it and does not mind all the rough ways.
Finally, there is the poke and run stunts that Ryan does on her. Every time he passes her on the chair, sarung or even the bed, he will poke her or rub her hair or wipe her face roughly. And not once did she scream or cry out loud. The most she will do is to make little sound to express her discomfort.
Really, I think they both know that they are somehow connected and hopefully, they continue to love and adore each other.