I am egyptian citizen & my sister is an Irish/...

 Please kindly note that according to the information given to us in your inquiry first and according to Irish law, the law allows adoption, especially with the presence of guardianship that facilitates the procedures for the adoption application, but what I would like to clarify, and according to the Irish nationality law, the adoption is not considered a reason for requesting citizenship, and to know the details, you can access this linkAdoption terms and procedures
On the one hand, and on the other hand, regarding nationality and acquiring it, the law clarifies the methods of obtaining citizenship through this link. You can also access it and know the details.Irish citizenship