These things are very personal. I have a mate who's extended family are Geordies, but he and his immediate family are all Londoners. They moved up here when we was a nipper so he and his brother are Newcastle fans but his older brother and dad are both Spurs fans. His derby's when we we play the Spuds and he's on edge like any of us would be the day before a mackem derby.
Although I've always thought the Tyne-Wear derby was important, I'm mates with a lot more mackems now, play football with a lot of them, too, so it's taken on more meaning in recent years.