The story is also commendable for having a parent and child successfully work together in a high-pressure startup. Many members of happy families would groan at the thought of working together, much less in such a chaotic context.
Sure, family businesses exist but processes are well established, company creation process involved only the parents. Friction is also minimized when the company is large enough to provide separation (i.e. relatives working in different depts/capacities that direct interaction with other relatives is minimized).
Excited to hear how this develops. It's often recommended not to go into business with your friends because the dynamic changes and your friendship can get replaced with a business relationship if you're not careful. There are also explicit hierarchies in business that might conflict with your friendship roles.
I haven't heard the same advice about not getting into business with your family, but I imagine similar challenges arise where you have to be conscious of turning off the business relationship over the holidays, etc.