No. Both Nikephoros and John were able to usurp imperial power while the legitimate Macedonian heirs, Basil II and Constantine VIII, were still minors, usually by conspiring with/being manipulated by/manipulating powerful court officials. Nikephoros is crowned co-emperor with Basil and Constantine in 963 only after being acclaimed by the eastern armies, and John (his nephew) only becomes emperor after Nikephoros is assassinated in 969. Both of them marry into the Macedonian house - Nikephoros to the empress regent, Theophano, and John to Constantine VII's daughter, Theodora - but neither of them have children, so any hereditary claim to the throne dies with them.

This marriage connection, however, despite the lack of any long-lasting results, may explain why Nikephoros and John are almost always grouped in with the Macedonians as a whole. Even any claim they might have had to acting as a kind of Lord Protector for Basil and Constantine doesn't (at least in my view) really substantially tie them to the dynasty as such, whereas marriages - however political or childless - certainly do, at least conceptually.