1) My sister seems (to) (be) (sleeping) on the sofa.
2) He (seemed) (to) (know) the doctor.
3) This plan needs (to) (be) (changed).
4) The song seems [(to) (have) (been)](不定詞・完了形) (popular) around the world in 2000.
= It seems that the song [was] popular around the world in 2000.
5) The castle is (said) [(to) (have) (been)](不定詞・完了形) (destroyed) about a hundred years ago.
= It is said that the castle [was] destroyed about a hundred years ago.
参考にしてください。