Jacob had 12 biological sons.Each of them had a tribe named after him except Joseph.
Jacob gave Joseph’s slot to his two sons- Ephraim and Manasseh.
“Now then, your two sons born to you in Egypt before I came to you here will be reckoned as mine; Ephraim and Manasseh will be mine, just as Reuben and Simeon are mine.Any children born to you after them will be yours; in the territory they inherit they will be reckoned under the names of their brothers.”
Invariably,Joseph had two tribes to himself.
Superficially what people see as loss may actually be a gain for you when seen from a deeper perspective.