(This is to people who have affectionate brother / sister and This would be harsh for people who love parents Even i love my parents and siblings)
I am youngest of all in my home . I have an elder brother and an elder sister. . But i would say if a mother or father shows affection on us it is mandatory on the other hand if brother / sister shows affection that is optional.Love your brother and sister more than your parents.
Generally Parents' biological and mental satisfaction leads to a child.It is their duty to show affection towards the child. They should take care of child. The same way since they show their affection it is the child's duty to show affection towards parents. This is a conditional affection. Think about a situation where a brother/sister showing affection towards a person. In what way and why should they show affection. Please do not think its a blood relation. Yes of course , but when they show it is an amazing thing and fortunate thing we should respect.
Finally i conclude good siblings should be respected more than best parents !!!