Matthew Gray (4) and Matthew Gray (7) maybe identical.
References
Jan 7, 1723/4 purchased 1/4 right in undivided lands from father John. May 3, 1725 sold to Robert Gray the 1/4 right received from father. Aug 25, 1739 sold land received from father John Gray. [Detroit Soc. For Gen. Research Mag. Dec 1952]