My daughter is a drug addict and had her son taken away by dcyf. He was very close to me. My ex has him and is isolating him from my side of the family. Can I adopt him?

This is not a simple yes or no question. You really need a lawyer. There are different processes in each jurisdiction. Also, we can't know the disposition of your daughter's rights to her child, or the father's rights. It makes a difference whether she voluntarily agreed to temporary placement, or if it was done by the court, or her rights were permanently terminated and so on. Even if the father is not known or involved, his rights have to be formally terminated as well before the child is available for adoption. Then there's no guarantee that even if he is eligible for adoption, that you would be the chosen adoptive parent.

To work through all the variables, you really need a lawyer. You can also, though, find out more by reaching out the county agency that removed him from your daughter's care and let them know, "I'm his grandmother and I would like to adopt and raise him". See what they say.

Under what conditions does your ex have him? That's the most key piece of information that we need to even begin to answer.