Olsson is a top summer target for Chelsea.
"Of course he is happy that his brother is with him at Blackburn but on the other hand he has other things to think about," agent Martin Dahlin told the Lancashire Telegraph.
"He has to keep on developing because he wants to keep his place in the Swedish national team. That means everything for him.
"I know the manager at Blackburn has said that he would like to keep all the players but playing in the Championship is not an option.
"He needs to play at the highest level to keep his place with the national team. Martin's ambition is to play in the top league somewhere and of course one ambition is to stay in the Premier League.
"There is already quite big interest in him. Five or six clubs are interested.
"There is interest from England and from other countries."