whosever可以引导让步状语从句和名词性从句。如果是让步状语，可以用no matter whose代词whosever; 如果是名词性从句，可以用anyone whose代替whosever.

无论这是谁的帽子，我希望他来认领。

Whosever hat this is, I wish he would come and claim it

No matter whose hat this is, I wish he would come and claim it

无论这是谁的自行车，你都可以用。

You can use the bike, whosever it is.

You can use the bike, no matter whose it is.

无论谁的家庭经济有困难，我都会帮助他。

I‘ll help whosever family has financial problems.

I'll help anyone whose family has financial problems.