My brother dated a married woman, who was then and still now lives with her husband, and she has said he has fathered 5 children, although her legal husband has signed all the birth certificates, knowing the children are not father by him, plus he has had a vasectomy. Now my brother has moved and moved on from her. But I have now been left in limbo cause I want to see the kids, I have always been able to see them but now the mother refuses.
So what are my rights and where do I start in order to gain visitation rights, and am I entitled?
I will be willing to submit DNA. But considering we have different father and same mother.
Right now the all her 7 children have been removed by DCF and placed in foster care. This is like the 6 time they have been taking from her. Making this that much harder, since I am no relation in their eyes I am not considered even for the temporary placement.
Do I have the right to pursue this even though my brother has not?

Unfortunately there are no laws stating that you have any rights to visit the children. You are not a grandmother, but an aunt. Grandmothers have rights, but aunts do not. Sorry. If the mother refuses to let you visit the children there is nothing you can do about this.