How to handle not liking your stepchildren....

I'm in a situation where I have one biological child from a first marriage, and now a step child from my second marriage. Despite the fact that both children are basically sweet, good kids, we fundamentally don't even like each other's kids. We get easily frustrated around them, become snappy, and are more likely to swiftly criticize the other's kid than our own. How do we get past this? I know developing love takes time, but developing "Like"? Is it possible to develop "like" when for the past several years we've spent at best tolerating the other person's child. Sometimes that has generated into active dislike and barbs towards the other person. Advice? Help? How do you handle this?