I've killed 2 or 3 orges and when I'm outside the cabin the green pointer indicates there is one more orge behind the house but it's not there. When I go inside the cabin the pointer turns red indicating my target is outside. A little help please.. Thanks

First of all, I think you are referring to Legacy Lost (the quest after Separated at Birth).

Occasionally, the three ogres wander off and when you arrive at Weatherleah there are no ogres to be found anywhere - even though you are told that they need to be killed. Check the surrounding area. They've been known to wander long distances to attack passing monsters and hunters - even as far away as Hackdirt and beyond. If you continue to have problems with this portion of the quest and you are on a PC, you can use the console command

setstage MS16A 40

to advance the plot to the next stage. If you are not on a PC it is advisable to load an earlier save until the ogres are there. Do not continue with other quests before completing this one because you will not be able to obtain the Escutcheon of Chorrol, the Honorblade of Chorrol, or begin the quest Sins of the Father.

Try wandering around the house, I frequently got this problem because I just jumped through the woods (not the "official way"). Backtracking through the road should update the quest to the appropriate stage.

If the arrow is pointing to a location where there is no Ogre, then it definitely seems like a bug. Maybe the Ogre fell in rock or through the ground or something. That doesn't happen very often. What happens more often with that quest is that an Ogre might wander off, sometimes chasing a deer or other animal.

In either case, if you level the area (ie go to a distant town) wait for over three days, then return, the cell the Ogre's are in should reset and you should be able to complete the quest without resorting to a console command.

It might be pointing to a spot by the well. If you've killed all three ogres, stand in the spot a few seconds and the quest will progress.

Oh, and the ogres probably don't "wander off" -- if the player speaks to Guilbert, but does not ask about Weatherleah, then speaks to a townsperson about it, the ogres won't appear at all.