The phrase "tenuous link" refers to a weak or thin connection between two things. It implies that the association between them is not strong or obvious. Full definition
There's always been a somewhat tenuous link between sexual appetites and our inherent craving for simple nourishment. (datingadvice.com)
A spectacular Day of the Dead opening is followed up by a drawn out plot with tenuous links to Bonds gone by. (timeout.com)
However, there are loads of other relations playing the game at an elite level, ranging from brothers to cousins to fathers to the slightly more tenuous link of brothers in law. (squawka.com)