Listen and empathize. Let people know you're listening by looking them in the eye and actually conversing with them. Empathize and think about what people are saying, or try to think of solutions to other's problems.
Thank others or be grateful even if you feel you deserve more or it wasn't something to deserve thanks.
In short, love others more. Do more for others. But I would say that there's a difference between "self-centered" and "self-serving." Centered implies that are preoccupied with your own concersns, always talk about yourself, can't relate with others, while serving implies that you take those preoccupations to action, usually at the expense of others.
tbh I have the opposite problem with codependency. Totally serving the other isn't all it's cracked up to be. There's a point where you'll just enable shitty people.
You may also find that you are not the problem, and it's just a bunch of narccists wanting to bitch, but if it's beyond your family and has happened multiple times I doubt it, and it would seem that you are the problem.