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I do have a few friends that do this stuff. I actually showed most of them how. Only one at the moment is doing anything that I would say is worthwhile. most of the others tire of it after a few weeks. But she stuck to it.
That little tangent was the first point. Affiliate stuff does require disapline up front. Sites do not build themselves (unless you have a good script and even then someone has to build the script ;) ). You may find that this whole thing is a moot point in a month or so.
That being said, I would sit down with your siblings now and explain just how many possibilities are out there. Niches within niches. Form a non-compete agreement. Tell them flat out that you have cornered this area and that they would make more money if they cornered a new area. It's the truth. You know you are good and they are behind in the learning curve. While they are getting their bearings, you will be breaking new ground. But if they take what they know to a different area, well, they don't have you to compete with and that makes it all the easier for them.
Maybe you have a few ideas that you just have not been able to develop. Pass them off to them. Perfect way to ease them out of your space. Tell them it's a great idea and you think you could make money off it, but you just don't have the time. If you are like me, this is true. You win, they win and everybody is happy.
Regarding my first posting, my siblings agreed to go into a different niche but what they really want is to work along side me and build a new site together so they can learn my skills and they will share any skills that they learn on their own. I know my competitors search my web site looking for things and techniques I am using, but it feels very weird when your siblings tell you they are breaking down your site and then they start informing you of all the different techniques that they see you are using. I even offered to pay them monthly just to do some basic paper work and research topics for me but they said they are more interested in working along side and learning.
Thanks everybody for sharing your opinions and experiences.