Since she let the oldest move in with his dad who legally only has every other weekend & holiday visitation. I have court ordered visits but she does not allow them. The father of my oldest doesn't allow me ANY contact with my son what can I do about this? I do not have money for attorney

You could try legal aid or you can do it yourself if you have all the documentation needed.

Take back your temp custody and demand the child back to live with you

Read the temp guardianship agreement. It should spell out how to revoke it. Do you have court orders giving you custody? Is there any court proceedings involving custody.

Why did you give your sis temp guardianship?

Also any question on law needs to include your general locale as laws vary by state.