Grandparents Right!?

Every one seems to have the wrong ideal about what I am saying.I am not trying to keep the baby a way from her father or his family,they have her 3 days a week.I was stating the fact that when it comes to them wanting to take the baby out of town ,they ask my granddaughter and not me.I was told that if while they are out of town I am responsible for that baby if anything happens to her cause i am the adult and since they are minors and are not married the baby belongs to the state ,unless someone files for custody of her,so after finding this out ,I went to file for custody .If Iam going to be held responsible for a child that they let minors make decisions for then I may as well have custody of her.She lives with me and my granddaughter and I did ask her if it was ok with her.I am looking out for the baby.I don't want her out in different climate and around a lot of people with all of the different viruses and diseases out here.She Is just an infant whos inmmune system is not strong