Re: Help Replacing Stringer on Steps
If the crack is from a poorly placed knot and the stringer is otherwise sound, you could sister it by bolting on a 2x6 to carry the weight. To be undetectable, you would have to get underneath and bolt it from the inside.
If the stringer has rotted or is split lengthwise, it's not a candidate for sistering and demo and replacement is the only way. You really need your front steps to be safe for liability reasons.
Remove not the ancient landmark, which your fathers have set.