Where to start?! I've been, what i would consider, very friendly with a few members from the same family for a while now. I feel I have helped them when needed and have been a good friend. I always would have had nothing but positive things to say about them all. Recently I have felt they have been "off" with me and I feel they are being awkward when face to face but yet they have invited me to an event and I have had a "normal" conversation recently with 1 of them via messaging. There is definitely something that is making them different towards me but I am certain I have never intentionally upset them and as I say I have nothing bad to say about them so I know I haven't spoken ill about them. I'm torn between asking them what is wrong and potentially opening up something that will only end up in a complete end to any pleasantries and letting it go and just pass myself in the belief that I've done nothing wrong and they have misread something or believed something someone else has said and therefore can "run on" if they have judged me so wrongly when they know me well enough to know I would never hurt them and am also approachable regarding any issues they may have.
There isn't enough info here to give you advice. This is a family so there might be something going on within the family that you are not privy to for good reasons. Maybe give them time and space or ask the one you're close to how they are. Don't assume it is about you.