For one thing, people need good models and examples. If children experience an environment where there is good middos, joy of Torah and Mitzvos, and ahavas yisrael, then the children will hopefully want to follow that. Of course, no one is perfect and there might be times when negative situations come up that might or might not have an impact. In that case, we should also teach people how to be strong despite negative situations. That’s why we need a strong foundation when we learn, so we are resilient and don’t let things tear us down.
Communication is key to a strong relationship with family. Plus, listening to how they feel, and being understanding and patient.
Also, pray to know how to help your family, because we can’t do it without G-d’s help. 🙂