The smell usually comes from two sources and unfortunately one of which you can’t do much about
Often the smell can be from wet hay - make sure you remove any wet hay and bedding daily.
What bedding are you using?
If fleece, make sure it is wicking properly and that the absorbent layer underneath is sufficient.
Otherwise, boars will scent mark, particularly if they are teenagers and hormones are high. There is nothing you can do about this, it’s normal for them to do so. However, cleaning too much can make them scent mark even more and therefore increase the boarly smells. It can help to only clean half the cage at a time, that way some of it always smells like them
You say a large cage, do make sure it is big enough (180x60 is recommended for two boys) as sometimes the smell can be made worse by a space which isn’t quite big enough