The examples that you mention are both metaphorical. I think in most cases of Swedish till- (Danish and Norwegian til-) there is actually a meaning of 'to, in the direction of', but frequently metaphorical.
Note that tillhöra is English belong to. What belongs to someone/something, should go to that someone/something.
Tillförlitlig is used about someone that you give your trust (lit) to.
Of course, it's not always as clear as in these cases, but I think it's good to think of till- as usually having the literal or metaphorical meaning 'to'.