Max George is said to be "distraught" over his grandfather's death.
The singer left The Wanted's wold tour to be with his family but he was left devastated after he didn't make it home in time to see him before he died.
An insider told the Sunday Mirror newspaper: "Max is incredibly close to his family.
"The death as really his him hard. He was distraught at not getting home before his grandfather died."
Max, 25, rushed home during the US leg of the band's tour due to "family matters", and was able to spend time with his family to help him through the difficult time.
Writing on their Twitter account at the time, the group said: "To let all our #TWFanmily know, @MaxTheWanted headed home to attend some family matters & won't be with us for the rest of the trip.
"We will crack on as a 4-piece so we look forward to seeing you all in Charlotte, Montreal, Buffalo, Green Bay & Chicago. Thanks all for understanding. Send positive thoughts @MaxTheWanted's way. [sic]"
Shortly after his departure, the band cancelled their European tour for 2014, citing "unforeseeable" schedule changes.
They said in a statement: "To all our fans in mainland Europe, we're really sorry but due to some unforeseeable changes in our scheduling, we're having to cancel our European tour dates in February/March."