I had a breakup with my ex boyfriend 6 yrs ago I then had a 9yr old daughter and 2 twin boys age 3, only my daughter was his biological child, no one has custody and because of threats he has remained there guardian till now, I am now a little older and all fear has subsided, and also have found out the children are currently living with his mother, both he and his mother won't let me take them still, what are my rights here with my sons

What and when were court cases done to gvie custody or guardianship to someone or anyway?

You will need to first find out what has been done in court, and hire an attorney to see about what custody you can get.

Why did you give them away at the time ? He has and had no rights to the children that are not his,

But if he has raised them for 6 years at this point they are more his than yours from a moral stand point