The happiness that we think comes from outside actually comes from within us, from within our own mind. It is the same with our problems. Actually, nothing comes from just outside. Everything depends on how one thinks. Although it may seem to come from outside one’s mind, those are only the conditions for problems to arise.
One way of thinking brings problems in life, the other way, one doesn’t see problems. You can read the book Transforming Problems and also His Holiness the Dalai Lama's books on the good heart and his teachings on patience.
You can mention to your brothers and sisters that whatever harm they think their parents are doing to them, if they had not done negative actions toward the parents in the past, there would be no reason for them to receive harm or any unpleasant experiences from the parents now. So, remembering karma helps one to practice patience, not to get angry and return the harm.
The parents of this life are very powerful objects in one’s life. They gave birth to this body, and even a small disrespect shown to them generates negative karma so heavy that the results are experienced in this life and also continue into the next life. Even a small service or respect shown to this life’s parents brings results so powerful that the experience of the results starts in this life and then goes on into future lives.
This happens from karma created with powerful objects, starting from one’s parents. This is one of the three types of karma. With the second type of karma, the results are experienced in the next life. The results of the third type of karma are experienced after many lifetimes.
A more powerful object than the parents are ordained Sangha, including arhats, who have been liberated from and are free of the control of delusion and karma. More powerful than numberless arhats is one bodhisattva, just because he or she has generated bodhicitta. If you look at one bodhisattva with a disrespectful mind, glaring at them, this creates more negative karma than taking an eye from all the three realms’ sentient beings. If one looks at a bodhisattva with a respectful, devotional look, this creates much more merit than offering jewels to all the beings in the three realms.
This is how powerful one bodhisattva is. More powerful than numberless bodhisattvas is one buddha. Still more powerful than all the buddhas is one’s own virtuous friend.
These are the powerful objects in one’s life, so a small act of disrespect to them brings very negative results. The more powerful the object, the more negative those results. Therefore, it’s very good that you want to try to help your brothers and sisters be in harmony with your parents, so that they don’t create negative karma with their parents.
If you get angry, it doesn’t help. It leaves an imprint in the mind, planting a seed that will cause anger to arise again continuously in the future. When you think someone is bad—that is, you label them “bad”— if you retaliate, instead of making others harm you less, you create the cause to receive more harm from others in the future.
Therefore, in order to help oneself and also to protect and give peace and happiness to others and to oneself, now and in the future, the wisest thing is not to get angry or harm them back. The best thing is to practice compassion toward them and toward others.