she's a ***** but I'd say you have no rights Im afraid
This is sad...but, the only "rights" that are law, that I'm aware of is parental and grandparents.....You could check with your local district court....there may be something in your areas law, that allows you to petition the court, if you have been a substantial influence in their lives, and she abruptly stops allowing you in their lives (not healthy for them)....Were you their caregiver? Did you watch them for her, on a regular basis? Stuff like that....Good luck...and I'm sorry your sister has chosen to use her children as pawns.....It is so unfair.
Butter up your sister-in-law and she'll come around.
i don't think you have any legal rights. sometimes it's hard to get along with in-laws, but in this case, if you want to see your nephews again, you'll have to talk it out with your sis-in-law. find out her reasons for banning you, listen to her, don't argue, apologize when necessary, and agree to whatever terms she outlines. she's in charge so you'll have to follow her rules. let her know you'll honor her wishes, even if it means supervised visits. it hurts too much not to get along with family, you'll just have to drop your pride and play really really nice. i hope this turns out well for you!
You have no rights. I suggest you make your own babies.