Welcome NinaMom!!! It is not impossible to bond several, but many times you do have to work out some major wrinkles with at least one. Some just won't work. If after a few months of bonding sessions everyday, and it doesn't work, then it may not be meant to be.
However, before you throw in the towel, you should try a stress method first, like taking them on a car ride for 20 minutes. Note: If a nasty fight has recently broken out, you may need to give it at least a few days before trying again.
You may even try just bonding her with the younger males first, and do the car ride method. The other board moderator also has some great stress method suggestions too.
Did you have a chance to check out the bonding section
of this site?
How old are the younger males?
Also, are they caged near each other right now? Have you done any switching of litterboxes yet? Or do you need help to start from square one?
Keep us updated!