Is it possible to get custody rights to see your child if you are their biologigal father and the child's mother signs over the rights for them to her mother as I was not in the country before she died

If you just want to see the child its called visitation rights. And yes, if the child was not adopted then your rights were not terminated and you can certainly go to court for visitation rights. You might even get some custody depending on the circumstances and local law.