The Avenging Seven

They were with Morgan.
Each time Morgan took six men into New Mexico to defend farmers from Bandits, there were some children. Each town children.
The total of the children that they had a relation with added up to "seven."
As time went on, those children grew up and they tested their knowledge and proficiency with guns, perhaps better than anyone else. Their education started as children apart from each other. Their time was well spent in the art of gun warfare.
One was taught how to become a great leader by "being" with your people.
Two are brother and sister that fought side by side while always looking out for one another.
Three riflemen matched any six-gun.
One is the fastest two-gun pistolero with not making a difference whether it be the left or right hand.
Sometimes they were edging for a fight even amongst themselves, whom was the fastest draw of their gun. Finally they came to the point of testing each other-they all had the same kind of teachers. But their excellence with firearms and the death of Morgan brought them together "after" officially meeting one another. It was then that they understood that seven is a "complete" or maybe "perfect" number when it comes to getting the job done.
They took on a whole army despite the fact of their battling with the notion of a "woman" being involved with them. Never-the-less that woman proved herself to all six men.
They had a great deal of encouragement as there were men from Morgan's group, older, but still knowledgeable, and willing to defend others because they cared. Excelling with the gun, they helped the best they could. Yes, the grown up children were efficient, yes they numbered seven.

This novel is the first book in the "Seven" series.