To Bear a Ring of Power...

[Kalimac]

I don't think Galadriel would have said such words to comfort a confused hobbit if they weren't true - what would be the good of giving him a comforting lie?

I agree with Witch King and Elvenglass - it was not even familial things, so much - Isildur was married, after all, and Bilbo's bachelorhood seems to have been established long before the Ring came along - but about the fact that a Ringbearer cannot trust a single soul, not even himself. You never know who might harbor intentions, or even who may not but who may eventually give in to pressure and try to take the Ring even though they swore quite honestly that they would not. It's a terrible amount of pressure, to say the least, and makes it more understandable as to why Frodo would distrust even Sam in Cirith Ungol. He doesn't know whether he can even trust himself, let alone anyone else.