Will I have rights to my stepson?

My husband and I are splitting up. And as we battle custody agreements and such, I can't help but put all focus on my stepson. I'm scared that my rights to seeing him will be taken away? I have been in his life before he was even one. His biological mother is not in the picture at all. She has no desire too. I have adopted him and I've been his only mom. He's my son, no doubt about it. Do I have the rights for shared custody with my husband? I know we will have shared custody with our daughter, I just want to be assured I can request the same for my son.