Thanks for your answer. My concern in detail

Because my kids are US citizen and my parents are not US citizen. In that case, the court is likely to award the kids to my hu*****and's father and his wife.
My hu*****and's stepmother is the same age as my hu*****and and has her own children. For what she has been doing in the past, we are convinced that she can not be trusted with raising my child and managing their asset. And my hu*****and's father, though a good person, is subject to her influence.
Can we draft a will or state in the trust to appoint my hu*****and's sister or even a friend to have the legal custody when neither of us is alive.