Stewart clan septs?

[Colonel MacNeal]

I am constantly looking online for information about my Scottish links through the Claghorn family, yesterday I found a tartan listed for Clan Cleghorn which is a variant spelling of the same family. While looking in this new direction I found a website that listed both Claghorn and Cleghorn as being septs of the Stewarts. Is it possible if no link to a family is found they use the Stewart as a default? Or is it that this family is a true sept of the Stewarts.
I will say that the Tartan Finder on Matt Newsomes website, I might add I find the Cleghorn tartan to be very attractive. It is numbered 4144 on the registry.

You can use the Royal Stewart, the Black Stewart, and the Navy Stewart as defaults anyway because they are universal tartans. So wear any of them with pride. Just don't claim to be a Stewie unless you're sure.
Cheers, ColMac