Franklin Richard is the natural born son of Reed and Sue. He is a mutant of impossible reality-altering powers, which have been present since he was a toddler. Fearful of his son's greater powers (psyche majors feel free to discuss in the comments), Richards decided that the only path to safety was to shoot his kid in the head with a laser that would shut down his entire mind while Sue is holding him in his arms.
Seriously, can you think of any incident that turns out well from approaching a mother cradling her son with a giant blaster rifle? Eventually Franklin overcome being comatosed by his father, and has somehow turned out to be a pretty well-adjusted kid despite being one of the most powerful creatures in the universe and being saddled with a dad who answers his physical development problems by shooting experimental energy weapons at him.
Did you know that early in his career Spider-Man wanted to join the Fantastic Four? It's true, and it's also perfectly understandable. The team was a great mixture of experience, Richards and the Thing, and youthful energy, Sue and the Human Torch. Plus they were already based in New York, so Spider-Man would've been able to continue his normal life.
When you think about it, Peter Parker would've been the perfect fit for the group. He was a science prodigy who could've used Richards' mentoring and resources to do all kinds of brilliant research, his optimism and wit would've offset the oft-melancholy Ben Grimm, his dedication to personal responsibility would've tempered Johnny Storm, and Sue could've helped him with his famous girl problems.
Know why it didn't happen? Because Reed Richards wouldn't pay him a salary. Richards is ridiculously rich from his many patents, and both Sue and Johnny come from significant money themselves. You've seen how Peter Parker lives, he would've been happy with a free place to stay, food, and enough money to keep him tights. He doesn't even need gas money. All told, we're willing to bet that Spidey would've taken the job for the equivalent of around $35,000 or less a year in modern dollars. The fact that a man who outright owned the top five floors of a New York City skyscraper wouldn't fork over what was probably spare change to him to recruit someone like Spider-Man is mind-boggling.