Fridging is when a love interest gets killed just to push the main character forward. It used to mean a woman getting hurt to make a man act. Now it covers any partner dying to pump up the plot.
Here’s the cold truth. A romantic loss is the only loss that actually justifies losing your head over it. If your boyfriend or girlfriend dies, that grief can spiral into obsession or a need for revenge. That is story fuel. Everything else is background noise.
An uncle, a child, a best friend, a parent, a teammate getting killed is not tragic nor is it enough to be sad and enough to motivate you to be a hero. Those losses might be a little sad but they do not automatically justify turning your life into this crusade against injustice. They are not dramatic enough to demand you drop everything and hunt a killer down.
So yeah, fridging as a device works because romantic love is one of the few things audiences treat as absolute.
Whenever there is a story about a main character who is depressed because their best friend, parent, or child dies, I just can’t get into it, and I’m always like, “Please get over it,” because this isn’t enough to be depressed over, and it’s not enough to want to become a good person.
The relationship with your kid should be deeper than with your partner. Nowadays, many people have far more partners during their lifetime than children - you’ll never know whether your partner will still be with you in 10 years, but it’s very unlikely that your child will not be yours anymore. Similar with parents.
I will say that family members who aren’t love interests typically don’t get enough time and characterization to make the audience care much about them.