It doesn't stop you. The misinterpretation of meaninglessness does however. It's meaningless either way if I love my family or hate them. There's no inherent reason I have to love in a specific way or it has to be aimed at my family.

There seems to be a bias where people who are raised to worship meaning and think it's inherent, once they understand it is not, a new value or fixed idea rises out of it.

There has to be inherent meaning in something otherwise I will not do anything.

It's more failed idealism rather than nihilism. You can't do anything besides doing it through your own drives or egoism. But nihilism frees you from constraining yourself so you don't think the all meaning is outside of you and inherent.

Do whatever you can, it doesn't matter either way. There's no fixed way to love either. It's a large neurobiological process that differs from person to person. I don't love someone because there beautiful, human, or cultured. That would be to love an abstraction, a nothing. I love them because it stems from my neurobiology, my egoism, because it makes me happy. I don't want to delude myself that there's some love outside of me that I have to tap into, nor is there any inherent reason I have to be happy. My emotions are valueless therefore I don't have to constrain myself to striving after certain emotions.