If the Parent's Aadhaar number or mobile number or Government Unique Id for the Father / Mother is updated as same then it will be considered as siblings.

Sibling profiles matching order      
India : 1.Parent Aadhaar No's,   2.Parent Mobile No's,  3.Government Unique ID's      
Other Countries : 1.Government Unique ID's,   2.Parent Mobile No's,  3.Parent Aadhaar No's