The thing is, none of us can choose our family, and the dishonest, untrustworthy, the thieves, murderers, rapists out there are all part of families. So effectively, we have a random chance of having family members we cant trust. In an ideal world, families would stick together and never betray one of their own, but life ain't like that, and like Dot said, human beings are fallible.
But we can and do choose our own friends and partners, so provided you are a half-decent judge of character, Id say you have just as good a chance of finding someone, or several people outside of family you can trust unconditionally, possibly even more than your closest family members.
My ex-gf couldn't trust me. Right from day one the paranoia and insecurity was obvious. I did nothing to warrant this, and over time, rather than getting better as I proved myself, it got worse. Turned out her ability to trust, well in fact her trust in human race had been obliterated from a very young age in ways Im not even gonna talk about. This was inflicted by family members.
Now the point I'm making is that in me, she found someone she really could trust. I would have never let her down. But we split a few months ago after 5 years together, ultimately because she still couldn't trust me. I loved the her to death and spent 5 years of my life proving this, but because of those so called "family" members, our relationship was tainted and eventually destroyed by an endless stream of unprovoked accusations, insults, suspicions and paranoia. And that mistrust and paranoia was not provoked by me, an outsider, but by family.
So in answer to your question Bob, No. We make our own way in this life, and ultimately, family are just who you are born into, and are lucky/unlucky enough to grow up around. The people you can trust are those who earn it, family members or not. Actions speak louder than blood.