So many single girls in the world, and you get attached to two in relationships?
Yes, there are boundaries. Respect other people's relationships. If someone tells you their relationship is 'okay' that doesn't give you the green light to read into it, draw the conclusion they're unhappy and therefore giving you the right to pursue them.
Think about it. Would you be okay with men actively pursuing your woman on the assumption she wasn't happy? If she left you, would you feel like he was obviously the better man and be happy for her? Doubt it.
Live as if you were to die tomorrow. Learn as if you were to live forever. - Mohandas Gandhi