oooh... personally (this is canon actually) i think the twins practiced kissing together........

rciel climbing into his baby brother's bed in the dark of night.. holding onto each other, slipping their hands under clothes to just touch and touch, to feel every inch of each other's skin.... their lips hardly part for more than a moment, breaths intermingling and filling the space under the blanket with an endless heat. it never processes that what they could be doing is wrong. their parents kiss all the time, they hear sweet proclamations and admissions of love and admiration.... it's the same, isn't it? they love each other too. rciel loves his baby brother and ociel loves his big brother. so it's only normal for them to hold and love each other the way mommy and daddy do, isn't it?