A trust can be set up for a family or for an individual. You (as the person creating the fund) can specify the terms of when the person is allowed to have access as part (after your death, when they reach a certain age, etc).
You can set up a family trust (your children or grandchildren) and make one member a trustee, who is in charge of seeing the shares divided and whatever terms are met by the individual. For example, my parents made me the trustee of our trustfund. I am to see to it that my sisters and my nephew (upon turning age 18) get their share. However, for my oldest sister (aka, loser-sister), I am not to give her a dime if she's (to my knowledge) on drugs or alcohol. So I would be completely within my rights to demand a drug test from her before signing the papers.
Of course, after all these years, I do not know if there is any money left in the trust, since my parents are still alive and are still in control of it. I haven't asked, because I don't really care. It's not mine until they die, and that's not something I look forward to.