Trying to be happy

I am trying so hard to be happy for my bother and his wife who are on the way to the hospital to have their second baby, but it is soooooo hard!!!!!!!!!!! I do not have the best relationship with my sister-in-law which has put a little distance between my bother and I, we use to be VERY close, but even with  hat I still Want to be happy for her but it is so HARD. Advice please!!!!