My grandsons have lived with me for almost a year. Their mother went to jail and it is undetermined how long she will be there. The boys talk to their mother on the phone 3 times a week. Her boyfriend, the supposed father, wants custody and said we will not see them again. The boyfriend said he was going to cut all ties with us. Do I have any rights to get to see them if he does get custody?

My grandsons have lived with me for almost a year. Do I have any rights to get to see them if he does get custody?

Yes- if I were you I would fight for sole custody. You have served as "De facto parent" for a year and that gives you good standing for custody/visitation rights.

I wish I was as sure as GV70 since you have been raising the child for a year, the court will take that into consideration, Next I guess you said supposed father since he is not on the birth certificate and has not done a DNA test. So he will need to file in court and prove he is the father. So why is he threatening is he asking for something or want you to do something so he will not do this ( form or blackmail )

In the US in some states Grandparents have laws giving them rights, in other states they do not.