Kori on Family Tree Circles

I'm researching my biological father's family history. His name was Craig Edwin MacDonald, born 1958. I can trace his mother Margaret Isabel MacDonald nee Donnelly (my grandmother's)family back to the mid 1500's but im stuck with his father and his siblings. From what i've gathered, he had a brother Steven Jon and a sister Heather-Rae. His father (my grandfather) was John Edwin MacDonald. Anyone able to give a lead as where i can follow that from? The resources i have, and that i can afford to access end there.
Any help would be great!