Question an individual part of two family trees

I created two family trees, one for both of my parents. working on my immediate family through the paternal lineage, I added my mom as wife of my dad, is there a way to make her part of the family tree I created for her family? Or is this not how it works? Does the tree just keep growing and expanding?

If so, what is the purpose of creating different family trees?

In most cases only one family tree is needed.  Start with you, add your parents, then the four grand parents, etc.

Some people work on multiple families, for instance a friend’s family where no cross over is going to happen.  Others may research their ancestors, but also do family name or regional, town, etc. research where there may be little or no cross over.  This is more advanced than simple “my family” single tree.  You could work on a group of people that “could be” family in a second tree, then merge them when you have proof they are related!

I have thousands of second, third, fourth cousins, that are many times removed from me in my single tree, along with my wife’s 100s of distant relations!  It is up to you what you want to record!  Some people just record direct family (only ancestors) based (starting with) on their children or grandchildren.  Others start with a specific ancestor and find all descendants!

Have fun.  That could be all that matters.  Welcome to webtrees!

> If so, what is the purpose of creating different family trees?

A common reason would be to apply different privacy rules to each tree.

For example, if you do not want your mother's family to be able to see your father's family.