All change is self-change, nobody can change us and we cannot change anyone else. However, we influence how others think and behave. We are always reacting to the people and circumstances around us and when people and circumstances change, we change our responses.
We must differentiate between the person and the person's behaviour towards us. Acceptance of the person is important while we creatively deal with any behaviour that is undesirable. Kindness can be the best weapon for change. People tend to behave automatically and are often not aware that they are creating problems with what they say and do.
You can be a mirror for them, reflecting what you observe to be the consequences of their behaviour. This can help them re-evaluate their responses.
Don't ask people to change or blame them for what they do, ask questions and get them thinking. When you get a person to think through what they do the process of transformation can take place.
People might want to change but they simply don't know how. You can't change a person to fit the idea of what you want them to be. The more you try to control others the more they seem to control you as meet with resistance.
When we change the way we see things, the things we see change. Expecting the best in people tend to bring out the best in them. We have the power to change people's hearts and minds when we change our heart and mind about them. Everyone has a light and darkness within them, we intensify what we focus on.
When you see a person in a certain way they become that way towards you, not necessarily to anyone else on the planet only to you. This is why you might not have got on with a person in a past relationship but that person got on excellently with the new partner.
What you need to change is yourself. You need to stop wanting to see a change in others in order to be happy. When you change you are in a better position to accept others or in a better place to let them go.