I currently have 5 and that's 1 too many.
I have my

Road/CX bike in aluminum
Tourer in steel
hybrid in parts
MTB 29er in aluminum
Pelago roadster in steel

What I really need / want in terms of simplicity of life and maintenance is

Steel road bike with at least 35mm tire clearance and all the possible eyelets / bosses. A multi use bike your could say
Tourer I have now
Steel Fat Bike for MTB'ing and bikepacking
Pelago Roadster for commuting and everyday getting around

And also the family cargo bike! A cargo bike is essential for car free living (although we still have a car, I just prefer to use it as little as possible)