what does "of that ilk" mean?

[MacMillan of Rathdown]

But he has raised his ugly head again, Scott, in the disguise of "The Scotsman." The big give-away was the post he made of his goat hair sporran, with the assumed crest of two birds of some sort.

Busted!

Sandy, in heraldic terms those are known as "birds of a feather" and originated with the Sobiesky-Stuarts, and have been passed down through a long line of fakes and frauds to the present individual who has adopted them "by his own hand" (or should that be purloined??), Lyon refusing to entertain his claims-- forged tombstone or not.