Welcome to IrelandXO's Croghan (Killummod & Killukin) Community.
The Mulveys came in to the Croghan area in the late 18th century. Killummod Mulveys are closely related to those in the civil parish of Killukin (Boyle) I'd highly recommend you join that parish group (as well as Tumna). The main family clusters are east of Croghan in the Drumlion area. Later branches elswhere originated from here.
I can give you more information depending on your particular family group.
Have you pinpointed a townland of origin yet? Either way, you are sure to find plenty of distant cousins in these parishes today.
If you can add your ancestor(s) to the parish database I'll be able to guide you more.