Why is love so messed up?

I feel sad and I don't know why.

Everything around me is delivering this message to me quite clearly:
Love never works out, relationships never work out, love is transitory and fleeting.

I think my sister and her boyfriend are going to break up. She called me earlier. She was drunk. She talks to me when she is drunk, which I don't mind because then I know she is being honest. She told me that their two year aniversary is coming up in a few days and she is not happy with their relationship. Apparently John says that he is and always will be "emotionally solo." He treats their relationship as shallow and superficial. He won't open up to her and doesn't listen when she opens up to him. I don't understand how she could have fallen in love with him if she wasn't close to him. I thought the two things went hand in hand. It's a shame, I like John, but I want my sister to have someone who knows and appreciates how unique and special she is.

After talking to my sister I started to look at other relationships around me. First my parents. I have never seen any evidence that they share any sort of connection. My mom is always nagging my dad and my dad is always appeasing my mom just to get her to shut up. It's possible that any romance they share is a well kept secret. My friends have all been in unhealthy relationships. Deborah's boyfriends have all been jealous and controlling. Her current boyfriend makes her call him all of the time just so he can guilt her and argue with her, yet somehow she is in love with him. Most of my friends are or have been in volatile or unhealthy relationships where they were "in love." I don't get it. Is this what will happen if and when I fall in love? I certainly don't want someone to argue with. I guess I will find out when it happens, assuming I eventually find someone.