Cryptomeria j., 'Sekkan'
Co-dominant leaders seem to be a common problem with this tree. The species doesn't seem to suffer the same problem,... at least in my experience.
Last winter an ice storm did significant damage to my garden, even to the natives. The ice just ripped apart this Cryptomeria j., 'Sekkan. I should have maintained a single leader, but never got around to it.
I think the problem is that it's planted in soil that's too good for it, causing unusually fast and lush growth. The soil has been liberally amended with horse stable manure and woodchips over a period of 25 years with a winter water table three feet down.
Here's a picture of another 'Sekkan' that's planted in a higher, drier, less fertile place, just a few yards away. Multiple leaders are not much of a problem with it. Both trees receive no supplemental water from me.
If you look closely you will see a larger than normal branch, going up, that needs to be removed. If I can get off the computer, I will do it today. ;-)
Can soil be too good for some conifers?
I think so.
As Ken says, "You can love a plant to death".