Usage of "chip off the old block"

Solution 1:

The phrase doesn't necessarily have to refer to a father any more. As the Phrase Doctor mentions, it means:

A person or thing that derives from the source or parentage.

The site does mention that the phrase is usually meant to refer to a father, but that it isn't the only meaning:

In 'chip off the old block' it is the parent, especially the father, that is being called the old block.

So, you can feel free to use it to refer to the similarity between a child and either of their parents. However, I wouldn't necessarily use it to refer to a child and another family member: it is more understood as referring so someone's parentage.