my girls are only 4.5mths old but they do things which i class as 'special moments' - they constantly seek each other out (nearly every photo we have of them together they are touching each other and now have started holding hands)

when isabelle had bronc and was hospitalised we had to pry lily off of her at every ob's check - she moved in the cot (they were only 10w old at the time mind you) so her head was against isabelle's heart

when lily is teething - isabelle reaches out and touches her to let her know its all ok

and like you the list goes on

it really does make my heart melt watching them - in a sometimes horrible world it's nice to know they will always have each other