It's not the reason, but it is a reason. The reason (for me) would be the principle of family coming first. But as is often the case, you can reconstruct deontological principles within a utilitarian framework.

For instance; if everybody sticks to the principle of murder being wrong despite the consequences, then there will be fewer misguided mass murderers, and this is better for society in the long run than everybody going around committing murders they believe to be justified by some end.